by Peggy Thomasndl.ethernet.edu.et/bitstream/123456789/1652/1/111.pdf.pdf · 2018. 9. 17. · Thomas, Peggy. Bacteria and Viruses / by Peggy Thomas. v. cm. Ñ (Lucent library of science

by Peggy Thomas

Bacteria andViruses

San Diego • Detroit • New York • San Francisco • Cleveland • New Haven, Conn. • Watervil le, Maine • London • Munich

© 2004 by Lucent Books ®. Lucent Books ® is an imprint of Thomson Gale, a part of the ThomsonCorporation.

Thomson is a trademark and Gale [and Lucent Books] are registered trademarks used herein underlicense.

For more information, contactLucent Books27500 Drake Rd.Farmington Hills, MI 48331-3535Or you can visit our Internet site at http://www.gale.com

ALL RIGHTS RESERVED.No part of this work covered by the copyright hereon may be reproduced or used in any form or byany means—graphic, electronic, or mechanical, including photocopying, recording, taping, Web dis-tribution, or information storage retrieval systems—without the written permission of the publisher.

Thomas, Peggy.Bacteria and Viruses / by Peggy Thomas.v. cm. — (Lucent library of science and technology)

Includes bibliographical references and index.Summary: Discusses various types of bacteria and viruses, methods of fighting diseases,and how bacteria and viruses can be used to benefit people and the environment.

ISBN: 1-59018-438-6

LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA

Printed in the United States of America

On cover: E.coli bacteria

Foreword 4

Introduction 7Swimming in a Sea of Microbes

Chapter 1 10We Are Surrounded

Chapter 2 25Early Discoveries

Chapter 3 39Fighting an Invisible Enemy

Chapter 4 54Emerging Microbes

Chapter 5 67Harnessing Invisible Power

Chapter 6 81The Future Under a Microscope

Notes 95

Glossary 97

For Further Reading 99

Works Consulted 101

Index 105

Picture Credits 111

About the Author 112

Table of Contents

4

“The world has changed far more in the past 100 yearsthan in any other century in history. The reason is notpolitical or economic, but technological—technologiesthat flowed directly from advances in basic science.”

— Stephen Hawking, “A Brief History of Relativity,” Time, 2000

The twentieth-century scientific and technologicalrevolution that British physicist Stephen Hawking

describes in the above quote has transformed virtuallyevery aspect of human life at an unprecedented pace.Inventions unimaginable a century ago have not onlybecome commonplace but are now considered necessi-ties of daily life. As science historian James Burke writes,“We live surrounded by objects and systems that we takefor granted, but which profoundly affect the way we be-have, think, work, play, and in general conduct ourlives.”

For example, in just one hundred years, transporta-tion systems have dramatically changed. In 1900 thefirst gasoline-powered motorcar had just been intro-duced, and only 144 miles of U.S. roads were hard-surfaced. Horse-drawn trolleys still filled the streets ofAmerican cities. The airplane had yet to be invented.Today 217 million vehicles speed along 4 million milesof U.S. roads. Humans have flown to the moon andcommercial aircraft are capable of transporting passen-gers across the Atlantic Ocean in less than three hours.

The transformation of communications has been justas dramatic. In 1900 most Americans lived and workedon farms without electricity or mail delivery. Few peo-ple had ever heard a radio or spoken on a telephone. Ahundred years later, 98 percent of American homes have

Foreword

Foreword 5

telephones and televisions and more than 50 percenthave personal computers. Some families even have morethan one television and computer, and cell phones arenow commonplace, even among the young. Databeamed from communication satellites routinely pre-dict global weather conditions and fiber-optic cable, e-mail, and the Internet have made worldwide telecom-munication instantaneous.

Perhaps the most striking measure of scientific andtechnological change can be seen in medicine and pub-lic health. At the beginning of the twentieth century, theaverage American life span was forty-seven years. By theend of the century the average life span was approach-ing eighty years, thanks to advances in medicine in-cluding the development of vaccines and antibiotics, thediscovery of powerful diagnostic tools such as X rays, thelife-saving technology of cardiac and neonatal care, andimprovements in nutrition and the control of infectiousdisease.

Rapid change is likely to continue throughout thetwenty-first century as science reveals more about phys-ical and biological processes such as global warming, vi-ral replication, and electrical conductivity, and as peopleapply that new knowledge to personal decisions and gov-ernment policy. Already, for example, an internationaltreaty calls for immediate reductions in industrial andautomobile emissions in response to studies that showa potentially dangerous rise in global temperatures iscaused by human activity. Taking an active role in de-termining the direction of future changes depends oneducation; people must understand the possible uses ofscientific research and the effects of the technology thatsurrounds them.

The Lucent Books Library of Science and Technologyprofiles key innovations and discoveries that have trans-formed the modern world. Each title strives to make acomplex scientific discovery, technology, or phenome-non understandable and relevant to the reader. Becausescientific discovery is rarely straightforward, each title

6 Bacteria and Viruses

explains the dead ends, fortunate accidents, and basic sci-entific methods by which the research into the subjectproceeded. And every book examines the practical appli-cations of an invention, branch of science, or scientificprinciple in industry, public health, and personal life, aswell as potential future uses and effects based on ongoingresearch. Fully documented quotations, annotated bib-liographies that include both print and electronic sources,glossaries, indexes, and technical illustrations are amongthe supplemental features designed to point researchersto further exploration of the subject.

7

Swimming in aSea of Microbes

Introduction

People do not realize how often they come into con-tact with bacteria and viruses. These microscopic

organisms are in the air, on the surface of this book,and inside people’s bodies digesting their last meal.Most people do not fully appreciate that microbes areresponsible for the oxygen they breathe, the healthyvegetables on the kitchen table, the pungent cheese inthe refrigerator, the clean clothes in the closet, and theclean water coming through the plumbing. Every as-pect of people’s lives and every part of the naturalworld is affected, for better or worse, by the actions ofbacteria and viruses.

And the worst comes in the form of disease. Eventhough the overwhelming majority of the encounterswith microbes go unnoticed, people are quick to re-spond when a run-in gives them a runny nose, fever,upset stomach, or more severe symptoms. Some bac-teria and viruses cause such pain and devastation thatthey become headline news. Every year novel microbesare discovered and new infectious diseases emerge. Itis not big news when a new bacterium is discoveredliving harmlessly in the soil, but it is broadcast whena virus mysteriously crops up out of nowhere and killsunsuspecting victims.

The first new disease-causing organism to emerge inthe twenty-first century was a virus that appeared in a

remote village in China. Researchers may never knowhow or why the paths of man and microbe crossed,but that fateful event led to the global outbreak in 2003of SARS (severe acute respiratory syndrome).

Researchers believe the virus’s story started inside awildcat called a civet. Through the natural process of ge-netic change, the virus gained the ability to infect hu-mans and may have seized the opportunity to do justthat when the civet was captured by a hunter or perhapsbought in a marketplace. Whatever the encounter was,it took only days for the first symptoms to appear. Atfirst just a few people came down with a fever and haddifficulty breathing. Soon dozens of others in the vil-lage grew ill. A doctor treated the patients as best hecould, but the mysterious illness would not respond totypical treatments. He had never seen anything like it.It was similar to the flu or pneumonia, but it hit hard


Patients in a Singaporehospital wait to betested for SARS. TheSARS virus was thefirst new disease-causing organism to bediscovered in thetwenty-first century.

and was deadly. Mysteriously the virus avoided childrenand attacked otherwise healthy adults.

Health officials do know that the doctor traveled toHong Kong, infecting many of the guests on the ninthfloor of a four-star hotel. One of those guests left the ho-tel and boarded an overseas flight to Toronto, Canada.Along with her luggage, she carried with her the SARSvirus. The microorganism proved to be an eager trav-eler. It unwittingly hitched rides inside its victims toTaiwan, Singapore, Vietnam, and dozens of other coun-tries.

In reaction to this outbreak, the medical communityand organizations such as the Centers for DiseaseControl and the World Health Organization mountedone of the fastest and largest responses in medical his-tory. Even so, in China alone, SARS infected more thanfive thousand people. It closed schools and businessesand threatened the lives of thousands of people wholanguished for weeks in quarantine. Outside of China,the virus weakened thousands of people and killed morethan eight hundred people worldwide. Economic ex-perts estimated that SARS cost Asian countries morethan $30 billion. Toronto, the largest city in Canada,lost $30 million a day because tourists and businesstravelers were warned to stay away.

When a microbe kills and causes the global panic thatSARS did, it is not difficult to imagine it as a malevo-lent microorganism out to get us. But disease is just theawful side effect of living in a sea of microbes, whichare as vital to the planet’s web of life as we are. Theemergence of a new disease should remind people howinterconnected human society is with these invisibleorganisms. Most of the time people are not aware thatthey exist. And unlike the clash with the SARS virus,the overwhelming majority of the encounters with mi-crobes are actually good for us.

Swimming in a Sea of Microbes 9

We AreSurrounded

10

Chapter 1

We are not alone. No matter how clean we are orhow healthy we feel, we carry around on our

bodies billions of microbes—microscopic one-celledorganisms called bacteria and viruses. Although theycannot be seen, microbes hide under fingernails, lurkbetween teeth, and live in hair. There are more than sixhundred thousand bacteria living on just one squareinch of skin, and an average person has about a quarterof a pound of bacteria in and on his or her body at anygiven time. There are more microbes on a person’s bodythan there are humans on Earth.

Viruses and bacteria are responsible for some of thedeadliest diseases in history, such as AIDS, the plague,and flu. And yet bacteria perform the most importantroles in maintaining life on this planet. “They [bacte-ria] protect us and feed us,” says Abigail Salyers, formerpresident of the American Society for Microbiology. “Alllife on Earth depends on their activities.”1 Bacteria arethe planet’s recyclers, plant nurturers, and undertakers.

Microbes have been found in almost every type ofenvironment. Some thrive in subzero Arctic ice, whileothers live in boiling undersea volcanoes. Bacteria havebeen found inside oil-drilling cores pulled from morethan a thousand feet down in the earth’s crust, and ithas been estimated that there may be as much as 100trillion tons of bacteria deep beneath the surface of the

earth. If all the subterranean microbes were broughtto the surface, they would cover the planet with a layerfive feet deep. Microbes have been discovered six milesbeneath the Pacific Ocean, where the pressure is equiv-alent to being squashed by fifty jumbo jets, as well asnineteen miles out in space.

Professor Adrian Gibbs of the Australian NationalUniversity asserts, “You can increase the probability offinding new things by looking in interesting places,like deep sea vents or thermal pools, but you can alsofind them in your own backyard.” 2 One teaspoon ofordinary soil contains 10 million bacteria, and one acreof soil can hold up to five hundred pounds of micro-scopic life. There is more unseen life than seen. Themass of all microbes on the planet is twenty-five timesmore than the mass of all other animals combined.The human race may believe it is at the top of the foodchain, but microbes are the food chain.

We Are Surrounded 11

Microbes can thrive inalmost anyenvironment, fromsubzero Arctic ice toboiling underwatervolcanoes.

Ancient MicrobesHow did these organisms become so widespread? Theanswer lies in the fossil record. Scientist J. WilliamSchopf found evidence of ancient microbes in rock sam-ples collected in western Australia in the 1980s. Theserocks proved that bacteria had been on Earth for morethan 3.5 billion years, long enough to adapt to nearlyevery type of environment. In his book Cradle of Life,Schopf notes, “These organisms are not only extremelyancient but surprisingly advanced, and show that earlyevolution proceeded faster and faster than anyone imag-ined.”3 Scientists have even discovered a strain of bac-teria that can survive blasts of radiation one thousandtimes greater than the amount needed to kill a humanbeing.


Bacteria and viruseshave infected humansfor thousands ofyears. Some Egyptianmummies bear scarsor other evidence ofviral disease.

Scientists have not found fossil evidence of ancientviruses and may never do so because viruses are sosmall. But researchers believe that viruses have beenaround just as long as bacteria have, or even longer.Deadly viruses may have played a part in the extinc-tion of the dinosaurs and are thought to have con-tributed to human evolution.

Historians do know that bacteria and viruses infectedhuman civilizations as far back as three thousand yearsago. The mummy of Egyptian pharaoh Ramses V hasthe telltale signs of scars caused by the deadly small-pox virus. The shriveled arms and legs of other mum-mies suggest that these people suffered from the poliovirus. And the Bible describes an ancient plague, rem-iniscent of anthrax, which caused “sores that breakinto pustules on man and beast.” 4

BacteriaOne reason scientists believe that microbes have sur-vived for so long is their simple structure. A bacteriumis a primitive one-celled organism. Like all living things,it grows, uses energy, makes waste, and reproduces allwithin one cell. A hard cell wall made of cellulose pro-vides support and protects the bacteria from antibioticsubstances, such as medicines, tears, and saliva. An in-ner lining, called the cell membrane, acts as the gate-keeper controlling what goes in and out. Some bacte-ria also have a sticky outer coat, called a capsule, thatallows the bacteria to stick to other cells.

Bacteria come in three basic shapes: Cocci (pro-nounced cox-eye) are shaped like little round balls;bacilli (buh-sill-eye) are rod- or stick-shaped; and spirilla (spy-rill-uh) form a spiral. Scientists estimate thatthere may be a million species of bacteria in the worldand more than five thousand different viruses, but onlya small fraction of these has ever been studied.

Some bacteria exist as individual cells floating ontheir own, while others cluster together to form pairsthat scientists call diplo. Several bacteria strung together


in a chain are called strepto, and when bacteria stick to-gether in clusters, they are referred to as staphylo.

Bacteria have a wide-ranging diet. Some bacteria arecapable of photosynthesis, just like plants. They maketheir own food from sunlight and give off oxygen.These bacteria are called cyanobacteria. Although theseaquatic organisms are often referred to as blue-greenalgae, that name is misleading because they are not re-lated to other types of algae.

Other bacteria absorb nutrients from the materialsthat surround them. There are bacteria that feed off ofwood, glue, paint, and anything dripped, dribbled, orleft out on the kitchen counter too long. Others eat iron,sulfur, petroleum, a variety of toxic chemicals, and evenradioactive plutonium. The bacteria that live in a per-son’s stomach absorb the nutrients from ingested food.A rotten spot on an apple is evidence that bacteria areeating. The sour smell of old milk is a clue that bacteriaare there. And the feeling of fuzzy teeth in the morningis evidence that bacteria are at work.

Although most bacteria cannot move about their en-vironment on their own, some have flagella, long whip-like tails that propel bacteria through a drop of liquid.One bacterium’s flagellum was recorded moving twenty-four hundred beats per minute. Other bacteria are notas speedy. They secrete a slime that allows them to slideover surfaces like a slug, or they move with the help ofcilia, tiny hairlike structures that beat wildly.

Bacteria move in response to their environment.While studying Escherichia coli (the bacteria that livein human intestines and can sometimes cause diar-rhea), researchers identified special structures callednose spots. These nose spots allow the bacterium tosense the presence of food and move toward it. Theyalso detect toxins and move away from them. Thesenose spots are extremely sensitive and can perceivetiny changes in the surrounding environment. It is thesame degree of sensitivity that would allow a personto detect the difference between a jar with 9,999 pen-


nies and one with 10,000 pennies. When food is de-tected, the receptors send a message to the flagella,which then beat rhythmically, carrying the bacteriatoward the increased concentration of food.

When food is not available, bacteria are capable of ly-ing dormant for many years in the form of a spore. Sporesof anthrax have been found in eighty-year-old museumdisplays; other bacterial spores have been brought back


to an active state from cans of meat that were 118 yearsold and beer that was 166 years old. Russian scientistseven claim to have brought back to life bacteria that wasfrozen in Arctic ice for a million years.

Spores are hard to find because they are microscopic.All bacteria are measured in nanometers. One nanome-ter is one-billionth of a meter. The period at the endof this sentence is about 1 million nanometers in di-ameter. The average bacterium, in comparison, is onlyone thousand nanometers across.

Bacteria are small, but viruses are even smaller. Toget an idea of their size, imagine one human cell thesize of a baseball diamond. In that cell, an average bac-terium would be the size of the pitcher’s mound. Buta single virus would be the size of a baseball. Scientistsneed to use a powerful piece of equipment called anelectron microscope to enter the world of the virus.

VirusesBacteria and viruses are often grouped together underthe heading of microbes, but there are vast differencesbetween them, and size is just one of those differences.While bacteria perform all of the functions necessary tobe considered a life form, scientists debate whether virusesare alive at all. For something to be alive it must eat, grow,make waste, and reproduce. When a virus is floatingaround in the air or sitting undisturbed in soil, it is nomore alive than a rock. But if that same virus comes incontact with a suitable animal, plant, or bacterium cell,it suddenly becomes active. A virus does not eat, but itgets its energy from the host cell it infects. It does notgrow in the sense that it gets larger, but it does reproduce.In fact, a virus’s sole purpose seems to be reproduction,and it cannot do that without the help of a living cell.

A virus is not even considered a true cell. It is sim-ply a tiny bundle of genetic material, DNA (deoxyri-bonucleic acid) or RNA (ribonucleic acid), surroundedby a protein coat. Both DNA and RNA are the mole-cules that contain coded genetic information. They


make up genes that determine what an organismlooks like and how it behaves. Unlike the DNA in ananimal or plant cell that is contained in a nucleus,viral DNA floats loosely within the protein coat, orcapsid.

Like bacteria, viruses come in many shapes and sizes.Many are multisided and look like a cut diamond.Other viruses are shaped like sticks, ovals with spikes,or tiny sausages. The deadly Ebola virus looks like apiece of looped string. Viruses that attack bacteria arecalled bacteriophages and resemble tiny lunar land-ing modules or alien spaceships.


Microbial MultiplicationMicrobes are experts at mass production. Bacteria re-produce through a process called binary fission. Onecell divides into two cells, each of which then divideinto two more. Each cell is identical to the mother cell.Most bacteria divide every two or three hours, somewait as long as sixteen hours, and others are capable


of dividing every fifteen minutes. One researcher esti-mated that if one bacterium reproduced every twentyminutes without running out of food or encounteringany toxins, it would grow into a colony of 2 millionbacteria within seven hours.

Viruses are just as productive, but they cannot do italone. Viruses need the reproductive mechanisms of aliving cell in order to multiply, but first the virus mustget inside the cell. A cell’s membrane is made out ofprotein molecules, and some molecules have speciallyshaped receptors, or landing sites, where other mole-cules with matching shapes can land and dock. Thislock-and-key system allows the entry of only certainmolecules that are necessary for normal cell function.For example, essential nutrients such as oxygen are al-lowed to pass through the membrane to one of manyof the cell’s powerhouses, the mitochondria. Nitrogenis received at different sites on the membrane and shut-tled through to be used in the assembly of various pro-teins.

But viruses have also acquired the key to specificcells. For example, the pneumonia virus is capable oflatching on to a human lung cell. The virus that causeshepatitis can infect human liver cells. The human im-munodeficiency virus (HIV) that causes AIDS is capa-ble of landing on white blood cells.

Once a virus attaches to a host cell, it inserts its ge-netic material in one of three ways. Some host cells arefooled into thinking that the virus is food. These cellspull the genetic material in just as they would pull inother nutrients. Other viruses have a sticky coat thatfuses with the cell’s membrane, and the genetic mate-rial enters that way. Other viruses forcibly pierce thecell’s membrane and inject their DNA into the host.

The genetic material from the virus hijacks the re-productive machinery of the host cell and provides itwith a new set of instructions to follow. The cell isnow programmed to make hundreds of copies of thevirus’s DNA or RNA instead of its own.


The virus then uses the cell’s enzymes, which aremolecules that control chemical changes, to build newcapsids and other proteins it needs to survive. Like agenetic factory, the host cell churns out viral parts thatare assembled into brand-new identical viruses. Allother cell functions are shut down to conserve energyfor producing as many viruses as the cell can stand.Some cells simply fall apart from exhaustion, andviruses tumble free. But other viruses actively dissolvethe cell membrane to get out. Stronger cells will fill upwith viruses until they burst like an overfilled waterballoon. The new viruses are free to infect other hostcells, a process that spreads the disease. This continuesuntil the virus is stopped or the host dies.

Microbes at WorkOther microbes can cause the death of their hosts too,but the vast majority of bacteria play a vital role inEarth’s ecosystem. All life on Earth is connected in aweb of relationships. Every creature, no matter howsmall, has a job to do, and microbes are the workhorsesof the living world.

Bacteria keep the planet’s life cycles turning. It is animportant job because the earth is a closed system.There is only a limited amount of the materials thatsustain all living things, and these elements—oxygen,carbon, hydrogen, nitrogen, phosphorus, and so on—have to be recycled again and again. Microbes are thekey players, chemists building, breaking down, and re-building chemical compounds for both animal andplant use. For example, animals breathe in oxygen andexhale carbon dioxide (CO2). Plants take in that CO2

and release oxygen that will be taken up again by an-imals. Microbes beneath the sea pump out about 150billion kilograms of oxygen every year, producing one-half of all the oxygen we breathe. This recycling processseems simplistic on the surface, but scientists are awedby the complexity of this assembly-line efficiency thatis required to keep the earth’s ecosystem cycling. If that


system were to stop, all the oxygen in the air would beexhausted within twenty years.

A similarly complex cycle occurs for nitrogen.Nitrogen exists in every living cell and is necessary forbuilding proteins. Although nitrogen is the most com-mon gas in the atmosphere, animals cannot use it inthat form. Animals get their nitrogen from eatingplants or eating plant eaters. Most plants are also un-able to take nitrogen from the air; they get their cell-building nitrogen from the soil. But most plants can-not get the nitrogen they need without the help ofnitrogen-fixing bacteria. These bacteria “fix” the ni-trogen by combining the nitrogen in the atmospherewith other elements to form organic compounds inliving cells. When these cells later die, the nitrogen,now in a fixed form, is readily available to the plantsthrough their root systems with the help of other bac-teria in the soil. In return, the plant supplies the mi-crobes with nutrients for their growth. Some bacteriasimply live in the soil surrounding the roots, but otherkinds of bacteria actually live inside the roots of plants.

Farmers rejuvenate their fields by planting nitrogen-fixing crops such as the pea plant. These plants havea powerful partnership with a bacterium called Rhizo-bium. As a young pea plant sends out its roots, it alsosends out a signal to willing bacteria. The bacteria inthe soil migrate to the roots, where they are surroundedby and eventually become part of the roots. An up-rooted pea or clover plant reveals tiny nodules or bumpswhere the bacteria are working to fix nitrogen for theplant. In return, the plant provides the bacteria with asafe home and the nutrients they need to live. This sys-tem is very effective. Researchers estimate that the bac-teria living in Asian rice paddies are capable of fixingmore than six hundred pounds of nitrogen per acre.

DecompositionAnother job of the microbial chemists is to free up theessential chemical compounds that are trapped in


plants and animals and would otherwise remaintrapped after death. Bacteria (along with fungi) are theundertakers of the microbial world. Bacteria help breakdown the dead matter in a process called decomposi-tion. If all the microbes were wiped out suddenly,nothing would rot. We would eventually be knee-deepin dead organisms.

All living things only borrow their atoms. They mustbe continually rotated and returned to the soil so thatother plants and animals can grow. The fertilizers thatpeople put on their lawns are nothing more than mix-tures of chemical compounds of phosphorus, nitro-gen, sulfur, and potassium, the same elements that arereleased into the soil by the decomposing activities ofmicrobes.

The Bacterial Buddy SystemJust as some bacteria form partnerships with plants,other bacteria form partnerships with animals. Oneof the most common relationships involves bacteriadigesting other animals’ food.

Ruminant animals like cattle, sheep, goats, giraffes,and camels are incapable of digesting cellulose, a tough,protective structural substance that forms plant cellwalls. Yet leafy greens are their prime food source. Theonly creatures known to digest cellulose are microbes,so the only way ruminant animals can get any nutri-tion from plants is to harbor a healthy amount of bac-teria in two of their four stomachs. The first two stom-achs in the digestive system of a cow contain billionsof bacteria that break down the cellulose into glucose,which the cow’s cells can use.

Humans rely on bacteria to digest the cellulose infood too. When babies are born, their mouths and di-gestive tracts are sterile; there are no microbes livingthere yet. Newborns have been protected from all in-fection, including beneficial microbes, by the placenta.But the first time babies are fed, they get the bacteriathey need to digest food for the rest of their lives.


Besides breaking down tough cellulose in a person’sdiet, the bacteria that live in the large intestine also pro-duce essential vitamins (K, B12, thiamine, and riboflavin)that humans could not make themselves. Studies of an-imals born and raised in a sterile environment showhow vital microbes are to survival. Without them a per-son would have a whole host of problems. Without vi-tamin K, which is necessary in the clotting process ofblood, a person would be prone to uncontrolled bleed-ing. Without vitamin B12, a person would suffer from ablood disorder called pernicious anemia. Scientists didnot realize the importance of bacteria in our digestivesystem until the development of antibiotics. They were


An electronmicrograph showsbacteria at workbreaking down foodin the humandigestive tract.

surprised to find that people developed digestive prob-lems when taking an antibiotic. The drug killed the“good” bacteria in the intestines as well as the “bad”bacteria that made them sick.

Viruses and EvolutionMicrobiologists are discovering new information everyday about the important roles bacteria play in theworld’s ecosystem. But no one has yet discovered ifviruses have a beneficial function. Recent studies sug-gest that viruses may play some part in the adaptationsthat change species over time. Geneticists have foundbits and pieces of viral DNA inside animal cells. Thesesmall fragments were probably left behind from a timewhen that animal was infected with the virus. Whilethe host cells were reproducing the virus’s DNA parts,the genetic material was pulled into the host’s genes.There they survived in the host’s cells and were passeddown to the animal’s offspring.

Geneticists discovered that this “junk” DNA accountsfor nearly half of a person’s genetic material, or genome.“People started to seriously consider that they [viruses]might contribute to evolution,”5 says John McDonald,a molecular evolutionist at the University of Georgia.Certain viral genes may have caused significant changesin human looks and behavior or even the branchingoff of man from ape 6 million years ago.

Bacteria and viruses have inhabited the earth muchlonger than humans have and were performing im-portant tasks long before we arrived. Microbiologistsare still learning the intricate connections that link themicrobe’s existence with our own. The smallest or-ganisms on Earth have had a powerful effect. Theyhave even altered the course of human history.


Early Discoveries

25

Chapter 2

It is impossible for the human tongue to recountthe awful truth. . . . The victims died almost im-mediately. They would swell beneath the armpitsand in the groin and fall over while talking. Fatherabandoned child, wife husband, one brother an-other; for this illness seemed to strike throughbreath and sight. . . . In many places . . . great pitswere dug and piled deep with the multitude ofdead. And they died by the hundreds, both day andnight.6

Agnolo di Tura chronicled this tragic yet commonoccurrence in Siena, Italy, in 1348. Called the Great

Pestilence, the disease was later known as the BlackDeath or bubonic plague, and it swept through Europewith frightening speed. Spread by the bite of an in-fected flea, the Yersinia pestis bacteria caused the mostdevastation recorded in human history. Within fouryears it killed one-third of the population of Europe,more than 25 million people.

The first symptom to strike a plague victim was a se-vere headache. The victim would grow weaker and even-tually too tired to walk. After about three days the lymphnodes in the victim’s armpits and groin swelled to thesize of goose eggs. These swellings, called buboes, gavethe disease its name—the bubonic plague. The victim’sheart would futilely try to pump blood throughout theswollen areas. Blood vessels broke, causing widespreadhemorrhaging that blackened the skin. Soon the patient

would cough up blood and the nervous system wouldcollapse, causing their limbs to jerk in fits of pain.

Once the lungs became infected, the disease couldbe transmittable from person to person through theair. At that stage, it was called pneumonic plague, andit swept through villages like wildfire. Within a weekthe patient was dead.

“I, Agnolo di Tura, buried my five children with myown hands. . . . And so many died that all believed itwas the end of the world.” 7

The world did not end, but it did change drastically.With more than a third of the population gone, la-borers were in high demand. Large tracts of land weresuddenly available for those once too poor to own


A nineteenth-centurypainting depicts theagony of plaguevictims. The BlackDeath of the 1340s,the worst outbreak ofplague in history,decimated Europe’spopulation.

property. The wealthy became wealthier still, as theyaccumulated the riches of their dead relatives. Thosewho survived the epidemic experienced a time of re-juvenation.

They also experienced a time of doubt and inquiry.The methods for dealing with the plague had failedmiserably. Many physicians began questioning the va-lidity of the ancient Roman medical philosophies thathad been the foundation of all their knowledge. Somebegan to study the human anatomy and develop newmethods of treating the sick. Rather than relying ontraditional methods, scientists began proposing newtheories of disease and experimenting to prove or dis-prove their theories. An invisible bacterium capableof killing millions changed history and opened thedoor to an era known for its startling new ideas—theRenaissance.

Smallpox and the New WorldMicrobes had an impact on history in the Americas aswell. The Caribbean island of Hispaniola had more thana million inhabitants when Christopher Columbuslanded there in 1492. Within twenty years, more than athird of the population was dead. Some died at the handsof cruel Spanish masters, others starved to death, but themajority of native islanders died from an epidemic dis-ease they had never seen before—smallpox.

Breathing in the invisible virus particles from an in-fected person’s sneeze or cough spread the smallpox virusfrom person to person. A week after inhaling these par-ticles, an infected person came down with a high fever,body aches, a headache, and chills. Soon the victim brokeout in a flame-red rash that grew fiery, raised, and blis-tered. These sores or pustules gave the virus its name,variola, derived from the Latin word for spotted. A per-son who survived might have scars or be permanentlyblinded. More severe cases that attacked the internal or-gans resulted in death. This devastating disease spreadquickly through a population that had no resistance.

Early Discoveries 27

The same thing happened when Hernán Cortés in-vaded the Aztec city of Tenochtitlán, where he and hissoldiers were soundly defeated by the Aztec army. Butas the Spaniards fled, they unwittingly left behind atime bomb in the form of a dead Spanish soldier in-fected with smallpox. Within weeks, the entire capi-tal was under siege by the smallpox virus, which killedone-fourth of the city’s inhabitants. According to oneSpanish priest, “In many places it happened thateveryone in a house died and, as it was impossible tobury the great number of dead, they pulled down thehouses over them so that their homes became theirtombs.” 8

The smallpox epidemic spread throughout Mexicoand helped the Spaniards defeat the Inca Empire aswell. Without the help of the deadly smallpox virusand other epidemics, the Europeans might not haveso easily conquered the New World. Smallpox also trav-eled to Brazil with the Portuguese, killing tens of thou-sands of Indians there, and marched north to NorthAmerica with the British, French, and Danish explor-ers, wiping out scores of Native American villages andentire tribes. The terror was universal. According toone French missionary stationed in Canada, “The con-tagion increased as autumn advanced; and when win-ter came . . . its ravages were appalling. The season ofHuron festivity was turned to a season of mourning.”9

Other infectious diseases caused by bacteria andviruses may not have had such a profound effect on theworld order as the bubonic plague and smallpox, butthey also weakened armies, wiped out villages, attackedthe poor, and cast blame on those who were different.

Punishment from the GodsWhere could these horrific diseases come from? Theymysteriously came upon a person, gripping him or herwith terrible symptoms and then quickly spread througha community. Ethnic and religious groups were oftenblamed for the disease.


Prior to the 1800s most people believed that epi-demics like the plague and smallpox were punishmentsfrom God. Describing the plague that hit Italy in 1347,the Italian writer Giovanni Boccaccio suggested thatthe plague signified God’s anger at people’s wicked wayof life. And when the Black Death ravaged England threeyears later, the archbishop of York said, “This surelymust be caused by the sins of men.”10

In India, people worshipped Sitala, the goddess of small-pox. Known as the “cool one,” she had the power to re-lieve raging fevers. In paintings and sculptures Sitala isportrayed dressed in red, riding a donkey. She carries acup of water to cool a victim’s wilting thirst and a broomto sweep away the disease. Although people bestowed


English nurses tend tosmallpox patients inthis nineteenth-century illustration.Although a vaccineexists today, deadlyoutbreaks of smallpoxhave been commonthroughout history.

her with offerings of cool drinks and chilled food, theyalso feared her, for Sitala could inflict the disease on theundeserving as well. It seemed only reasonable to blamethe mysterious illness on a higher power. After all, noone could see another cause.

The earliest written record suggesting that invisibleliving things might cause illness came from the Romanwriter Marcus Terentius Varro. In the first century A.D.he wrote, “Care should be taken where there areswamps in the neighborhood, because certain tinycreatures which cannot be seen by the eyes breedthere. These float through the air and enter the bodyby the mouth and nose and cause serious disease.” 11

Microbes Come into ViewPerhaps Varro was not the only one who suspected thata living organism invisible to the naked eye could ex-ist, let alone cause the deadly destruction that plaguedhumankind. But it was not a popular thought. Therewas no evidence that these tiny creatures inhabited theworld until a curious amateur scientist named Antonivan Leeuwenhoek saw them for the first time in 1676.

By profession, Leeuwenhoek was a draper (a clothdealer) who examined threads for flaws with a magni-fying glass. His fascination with magnifying lenses andthe world they brought into view led him to experi-ment with single-lens microscopes he made himself.While others used microscopes that enlarged objectsonly ten times their size, Leeuwenhoek’s microscopecould magnify up to 270 times. His lenses were sofinely made that experts today still are not sure howthey were constructed given the technology of the sev-enteenth century.

What Leeuwenhoek saw under his microscope wouldopen up a new field of science called microbiology. Afterlooking at the matter he picked from between his teeth,Leeuwenhoek recorded for the first time the presenceof what are now known as bacteria. He described themas “animacules, very prettily a-moving. The biggest sort


had a very strong and swift motion, and shot throughthe water like a pike does through the water; mostlythese were of small numbers.”12

Although Leeuwenhoek was the first person to de-scribe bacteria, the scientific community did not takehis observations seriously. In 1676 the secretary of theRoyal Society in London, wrote to Leeu-wenhoek: “Your letter . . . has been receivedhere with amusement. Your account of myr-iad ‘little animals’ seen swimming in rain-water, with the aid of your so-called ‘mi-croscope,’ caused the members of thesociety considerable merriment when readat our most recent meeting.” 13 The mem-bers of the Royal Society declined to pub-lish Leeuwenhoek’s observations until 1683,when they received more evidence. In themeantime, Leeuwenhoek continued to studypond water, spittle from an old man, in-sect larvae, and even the spermatozoa insemen. Leeuwenhoek brought the worldbeneath the microscope into view, but itwould take one hundred years before theseinvisible creatures would be linked withdisease.

Putting It All TogetherThroughout the 1860s, two scientists, LouisPasteur of France and Robert Koch ofGermany, working independently, collectedconvincing evidence that infectious diseaseswere caused by microbes and not by evilspirits or the wrath of God.

Pasteur was a chemist and microbiologistworking in France. In his studies of winemaking for the wine industry, he learnedthat microscopic bacteria and yeast organ-isms caused fermentation, the chemicalbreakdown of carbohydrates into carbon


In the seventeenthcentury, Antoni vanLeeuwenhoek inventedthis powerful single-lens microscope.

dioxide and alcohol. He went on to identify the mi-croorganisms that caused food to spoil and decompose.Before his discovery, people assumed that spoilage wasthe natural result of chemical breakdown over time.Pasteur found the microbes in milk that caused it to spoiland also devised pasteurization—the process of heatingmilk to a certain temperature at which harmful bacte-ria are killed.

After Pasteur’s success in the wine industry, the silkmanufacturers of France consulted him about the mys-terious deaths of their prized silkworms. Pasteur iden-tified two different bacteria that caused the deadly silk-worm disease. Pasteur’s work provided the world with


Anthrax bacteriainfect lung tissue. In aseries of laboratoryexperiments withmice, Robert Kochwas able to isolate thedeadly anthraxbacterium.

convincing evidence that microorganisms cause dis-ease, a concept that became known as the germ the-ory. Around the same time in Germany, medical doc-tor and researcher Robert Koch was also putting someof the pieces of the bacterial puzzle together.

Robert KochKoch was experimenting with ways to grow bacteriain the lab when he developed the process for growingbacteria that is still followed today. By using a gelatin-like substance called agar, which is made from seaweed,rather than blood or tissue from an animal, pure bac-terial cultures could be grown without contaminationfrom other blood or tissue cells. Koch’s assistant, JuliusPetri, created a covered shallow glass dish to hold theagar and the growing culture. Today this commonlyused piece of lab equipment bears his name—a petridish.

Another problem Koch struggled with was makingbacteria more visible under a microscope. Some bac-teria are very difficult to see, especially if they aremixed with other cells. Through experimentationKoch found that bacteria absorbed a dye made fromcoal tar, called aniline dye, which made them easierto see under the microscope.

At the time Koch was perfecting his lab techniques,anthrax was a common and debilitating disease that at-tacked cattle and sheep throughout Europe. Parts ofGermany were hard hit by the disease, and Koch set outto isolate the bacterium that caused it. He injected micewith blood taken from the spleens of infected animalsand observed how the disease worked as he transferredit from one mouse to another. His study of disease ledhim to write the criteria that are still used to determineif a microorganism is the cause of a disease. CalledKoch’s postulates, these criteria state that a pathogenic(disease-causing) organism must be present in everycase of the disease. This organism can then be grown,or “cultured,” outside the body. An animal inoculated


with the culture would develop the same disease. Theorganism could then be taken from that infected ani-mal and cultured again.

Koch went on to isolate the bacteria that caused tu-berculosis and chicken cholera, and Pasteur used Koch’slab methods to expand on his work with anthrax. Inorder to create a vaccine for sheep, Pasteur weakenedthe anthrax bacterium by growing it in the lab athigher temperatures than normal. When this weak-ened bacteria was injected into a healthy animal, itprevented infection from the virulent anthrax bacte-ria and became an effective vaccine. Pasteur went onto create a vaccine for chicken cholera and rabies.

By the end of the nineteenth century the germ the-ory was accepted as a scientific principle. Only oneproblem remained. For some diseases, no microor-ganisms could be found.

What Could Be Smaller than Bacteria?Although Pasteur created a vaccine for rabies, he neversaw the organism that caused this dreaded disease.Many other scientists who worked on plant and ani-mal infections assumed they were looking for bacte-ria, but they would never find them. What they didfind was something smaller and more puzzling.

In 1886 Adolf Mayer, a German scientist, was re-searching the tobacco mosaic disease, so called becauseit left the leaves of the tobacco plant shriveled andmottled. Mayer believed that the disease was causedby a bacterium, but he failed to isolate the elusive or-ganism. In 1892 Russian scientist Dmitri Ivanovskiruled out the possibility that a bacterium caused allthe damage to the tobacco plant. He suggested that asmaller pathogen must be at work, possibly a toxin.It was not until six years later that Martinus Beijerinck,a scientist from the Netherlands, showed that the dis-ease was indeed caused by an infectious agent smallerthan any other life-form known.

Ivanovski and Beijerinck performed similar experi-ments. They pressed juice from infected plants through


filters so fine that they removed all bacteria. When thisfiltered liquid was rubbed onto a healthy plant, itcaused the leaves to shrivel and discolor. Both scien-tists discovered that the plant juice could be dilutedmany, many times and still cause disease. And althoughthey suspected a bacteria-like organism might be atwork, it could not be grown separately in a petri dish.

Where Ivanovski and Beijerinck differed was in theirconclusions. Beijerinck believed that whatever passedthrough his filters was some kind of an infective agent


Dutch botanistMartinus Beijerinckwas the first scientistto identify viruses,infectious microbesthat are even smallerthan bacteria.

other than bacteria. He did not believe it was simplya toxin, as Ivanovski suggested. Beijerinck filtered anddiluted the infective liquid again and again until hewas left with such a weak substance that if it were atoxin, it would no longer harm the plant. But whenthis diluted substance was rubbed onto a healthy to-bacco leaf, it shriveled and the disease spread to otherparts of the plant. Attempts to grow the organism inthe lab failed. Whatever it was, the infective agentwould grow and spread only inside plant cells.

In 1898 Beijerinck wrote his conclusions. Using theLatin term for poison, he called the elusive particle afilterable virus. He showed that although it could notbe seen, the virus was an infective agent that was notconducive to being cultured in a lab. In his paper heobserved, “The contagion, to reproduce itself mustbe incorporated into the living cytoplasm of the cellinto whose multiplication it is, as it were, passivelydrawn.” 14

Building on Beijerinck’s virus theory, new discover-ies were made in rapid succession. That same year,Friedrich Loeffler and Paul Frosch discovered the virusthat caused foot-and-mouth disease, which had beenkilling cattle throughout Europe. They collected pusfrom the sores of infected cattle and passed it througha filter. They did not find a bacterium, but they did dis-cover that when the so-called filterable virus was in-jected into a healthy animal, it caused the disease.

It was not until 1900 that a filterable virus was dis-covered to cause human disease. Yellow fever had beenrampant and troublesome throughout Central andSouth America. It caused almost insurmountable prob-lems for the builders of the Panama Canal. Cuban doc-tor Carlos Juan Finlay suspected that a mosquito, Aedesaegypti, spread the disease. But this idea did not receivemuch attention until U.S. Army doctor Major WalterReed traveled to Cuba and conducted medical experi-ments. He discovered that the disease was caused by afilterable virus and confirmed that a mosquito was in-


deed the vector (it carried the virus from person to per-son).

Fifteen years later brought the discovery of a virus thatinfected bacteria. It was called a bacteriophage (bacteriaeater). The definition of a virus was taking shape—anorganism that could be passed through the finest filterand still cause an infectious disease in plants, animals,humans, or bacteria. The organism, however, could not


be seen and could not be grown in a laboratory. It wasnot until the 1930s that scientists got their first glimpseof their smallest enemy.

Viruses Come into ViewImprovements in microscope manufacturing did nothelp the search for viruses until a revolutionary ma-chine was invented. In the 1930s German researchersMax Knott and Ernst Ruska created the electron mi-croscope.

Instead of using an ordinary beam of light to illu-minate an object, the electron microscope uses elec-trons, which are accelerated in a vacuum until theirwavelength is extremely short. The beams of these fast-moving electrons are then focused on cells. The elec-trons are absorbed or scattered by the cell’s parts andform an image on an electrosensitive photographic plate.This technique allows the microscope to magnify an im-age up to 1 million times.

For the first time scientists could see the shape ofviruses. But the electron microscope still did not revealwhat a virus was made of or how it was constructed.That breakthrough came in 1932, when chemist WendellStanley used a technique called X-ray crystallography totransform the tobacco mosaic virus into a crystal. Thiswas an amazing feat. Because crystallization is a charac-teristic of a mineral, a nonliving thing, Stanley’s achieve-ment proved that a virus is not a typical living organism.It is essentially a chemical molecule, a protein, withminute bits of genetic material. This discovery wonStanley the Nobel Prize in Chemistry.

The bulk of what was discovered about microbes inthe early years of microbiology was through the studyof disease and disease-causing bacteria and viruses.One prime goal was finding a way to destroy them.


Fighting anInvisible Enemy

39

Chapter 3

Humans have evolved along with bacteria andviruses for millions of years, so it should be no

surprise that the human body has developed a systemof keeping the harmful microbes out. The first line ofdefense is the skin, which is a sheath of closely inter-locking cells. Sweat and oil glands under the skin se-crete acids that prevent the growth of microbes, andharmless bacteria that normally live on the body de-fend their territories against foreign bacteria.

The nose, mouth, and throat are common sites of at-tack, but fragile membranes and layers of sticky mucusthat are toxic to harmful microbes protect them. Tearsand saliva also contain antiseptic substances. Bacteriaand viruses are sneezed out, coughed up, and cried outof the body. If microbes make it through these barriers,they are swallowed. Most will not survive in the stom-ach’s acid environment or the toxic world of the in-testines. The beneficial bacteria that reside there willfight off potential competitors.

Our Internal ArmyA cut on the skin is a way in for some opportunistic mi-crobes, but the body quickly fights back with an in-flammatory response. Injured cells release histamine, achemical that causes blood vessels near a wound to swell,which brings more blood to the area to aid healing.

Blood quickly clots to seal off the cut and prevent morebacteria from getting into the bloodstream and spread-ing further into the body.

Injured cells also release a chemical that attractsbacteria-eating white cells called phagocytes. Phagocytesengulf any bacteria they encounter until they are sofull they die. Any bacteria that manage to get pastthe phagocytes will be carried to other parts of thebody. The body’s immune system is alerted and sendsout lymphocytes, or white cells. There are about 2trillion lymphocytes patrolling a person’s bloodstreamand lymph system at any given time. They standguard in the spleen, tonsils, and lymph nodes and de-tect all foreign invaders such as bacteria, viruses,fungi, and transplanted organs.

When a foreign invader is detected, the lymphocytesdivide and create antibodies to kill or neutralize the in-vaders. Antibodies are chemicals that target and destroyonly one type of invader. For example, an antibody sentout to fight against the pneumonia bacterium cannotfight a salmonella bacterium. It takes about a week togenerate enough antibodies to fight a disease. In thattime, it is a race for survival between man and microbe.

The immune system has an ingenious way of re-membering past battles so that this life-and-death strug-gle does not happen again. Lymphocytes create mem-ory cells that circulate through the body ready to battlethe old enemy. If a person comes down with the samestrain of pneumonia a second time, the memory cellskick into maximum production immediately. Somememory cells last a lifetime, which provides immunityagainst that disease for the rest of a person’s life. Thatis why a person who has had chicken pox will not getit again. This amazing immune response is the princi-ple behind vaccinations.

Ancient Asian SecretsSmallpox ravaged Asia for generations, yet as early asthe eleventh century there was a method of fighting


smallpox called ingrafting. No one knows how it wasdeveloped, but over time, a treatment was devisedwhere pus from the sore of a person with a mild caseof smallpox was smeared into a scratch on the arm ofa healthy person. The person who was ingrafted usu-ally developed mild symptoms but recovered quickly.They never caught smallpox again.

This technique spread to Europe with the help ofLady Mary Wortley Montagu, the wife of the British

Fighting an Invisible Enemy 41

BacteriumAntigen

Lymphocytes

Lymphocyte locks onto antigen.

Lymphocyte multiplies rapidly.

Antibody locks onto bacterium, marking itfor destruction.

Memory cell

B cell

The surface of germs such as bacteria carry markers called antigens, which enable lymphocytes to identify invading germs. Each lymphocyte recognizes a specific antigen, just as a key fits a lock.

When the lymphocyte recognizes bacteria by their antigens, it divides again and again to produce memory cells and B cells. Memory cells memorize the antigen, so that in any future invasion the body can react quickly.B cells make and release chemicals called antibodies. These target new invaders, locking onto their antigens. In this way they disable the invading bacterium and mark it for destruction by other cells.

Antibody

The Immune Response

ambassador living in Turkey in 1716. After witnessingthis procedure, she had her three-year-old son ingrafted.She brought news of the technique back to England,where it was called inoculation. The procedure was notwidely used because, although it was successful, therewas a risk that the patient could develop a severe caseof the disease.

The First VaccineOne boy who was inoculated was eight-year-old EdwardJenner. He survived the painful procedure and grew upto be a country doctor whose keen observations led tothe first vaccinations.

In 1796 Jenner noticed that young women whomilked cows sometimes became infected with cowpox,a disease that caused sores on a cow’s udders. The girlswould get painful sores on their hands, but the diseasewas not fatal. Once the girls caught cowpox, they neverbecame infected with smallpox.

In May of that year Jenner performed his first cow-pox experiment. He took fluid from a sore on the handof dairymaid Sarah Nelmes and inoculated a healthyeight-year-old boy named James Phipps. Within a fewdays James came down with a fever and a small sore.On July 1, believing that the cowpox inoculation wouldprevent the development of smallpox, Jenner inoculatedJames with matter from a smallpox patient. Nineteendays later Jenner wrote, “The Boy has since been inoc-ulated for the Smallpox which as I ventured to predictproduced no effects. I shall now pursue my Experimentswith redoubled ardor.”15

Jenner went on to repeat his experiments and pub-lished his results, calling his technique vaccination andthe matter taken from the cowpox sore a vaccine (de-rived from vacca, the Latin word for cow). In a letter writ-ten to a friend, Jenner predicted, “The annihilation ofsmallpox—the most dreadful scourge of the humanrace—will be the final result of this practice.”16 Jennerwould never know how accurate his prediction would


become. He also would never know how his vaccineworked or even what kind of organism he was actuallyfighting against. That information would not come formany more years.

How Vaccines WorkVaccines work by using our own natural defenses. Aninjection of a weakened virus or a part of a virus is justenough to trigger the lymphocytes to create memorycells. If the virus invades again, the body is able to fightit with ready-made antibodies before a serious infectiontakes hold. Vaccines may be made with dead microbesor parts of dead viruses. Some are made with living mi-crobes that are weakened and rendered harmless butare still able to elicit an immune response.

Rabies VaccineLouis Pasteur had created a successful vaccine forchickens, another for sheep, and he had been exper-imenting on a rabies vaccine for dogs, but he had notdeveloped a safe vaccine for humans. But that did notmatter to the mother of nine-year-old Joseph Meister,who took her son to Pasteur’s office in 1885. A maddog had bitten Joseph. Rabies is a horrible disease thatinfects only mammals. The virus attacks the nervoussystem and infects the brain, causing a difficult andpainful death.

Pasteur knew that a weakened germ worked as a vac-cine against other diseases in animals and believedthat a similar treatment for humans should workagainst rabies. He injected Joseph with the weakenedvaccine and increased the dose daily. After fourteendays Joseph Meister was stronger and had made his-tory. He became the first person to survive rabies.

More VaccinesPasteur’s success inspired a concerted effort to developvaccines for other dreadful diseases, but it did not happenquickly. Max Theiler created a vaccine against yellow


fever in the 1920s, and Jonas Salk and Albert Sabin pro-duced polio vaccines in the 1950s.

Today, there are vaccines for mumps, rubella,measles, tetanus, chicken pox, flu, and other once dan-gerous diseases. But there are many viral infectionsthat the medical community cannot prevent with aninjection. For example, there are too many strains ofthe common cold to create an effective vaccine, andother viruses mutate too quickly. A virus can alter itsouter protein coat so that antibodies and vaccines thatonce worked on the virus are no longer effective. Even


Vaccine Skin

Harmless germ

Injecting vaccineA person is injected with a harmless form of the germ,which does not cause the disease.

Antibodies are madeAlthough the germ is harmless, the body still recognizes it andmakes antibodies against it.

Fighting infectionIf the body is invaded by the disease-causing form of the germ, the immunesystem responds immediately with huge numbers of antibodies to destroythe germ.

This type of immunization uses a form of the disease-causing germ that has been slightly altered to stop it fromcausing the disease. The person receiving it will not become ill, but he or she will produce antibodies againstthe pathogen that does cause disease. The body will do this every time it is threatened by that germ.

Antibody locks onto germ

Antibodiesfighting disease

The Vaccination Process

a slight difference can mean that a person’s memorycells would not recognize the virus, and the antibod-ies that a person’s immune system created in the pastwould be powerless against this new strain.

The First AntibioticsIt seems ironic that medical researchers were success-ful in developing a preventive medicine for viruses,which were unknown to science and unseen by man,but were not able to fight off known bacterial infec-tions. The key was finding a way to kill a bacteriumcell without harming human cells.

The first breakthrough came in 1910, when PaulEhrlich, a German scientist, discovered that an arseniccompound killed a spiral-shaped bacterium called aspirochete that caused syphilis. His discovery was in-spired by Robert Koch’s work with aniline dye. In ameeting in Berlin, Ehrlich heard Koch describe howhe used the dye to identify the tuberculosis bacterium.When Koch applied the dye, it stained the bacteriacells, making them easier to see under a microscope,but it also killed the microbes.

Ehrlich experimented with many other dyes andchemical compounds before he achieved success witharsenic compound 606, which was dubbed “the magicbullet.”

How Antibiotics WorkEhrlich’s compound was called a magic bullet because,like other antibiotic agents, it specifically targeted thesyphilis spirochete. Antibiotics are simply chemicalsthat react with other chemicals. Every cell, whether itis human or bacterium, is also made up of chemicals.The cell’s membranes are covered with receptor sitesthat allow the cell to react with or take in other chem-icals. In order for an antibiotic to work, it must havethe right chemical makeup, or key, to fit the chemi-cal makeup, or lock, at the receptor site on the bac-terium. But the antibiotic’s chemical key must not fit


the receptor sites of other cells in the patient’s body.If it does, then it would cause adverse side effects.

Each kind of antibiotic attacks a bacterium in a dif-ferent way. Some, like penicillin, stop the bacteria fromforming a cell wall. Other antibiotics interfere withthe bacteria’s ability to make essential nutrients, suchas folic acid and other proteins, while others stop thebacteria’s DNA replication.

PenicillinThe power of microorganisms can be harnessed to healas well as harm. This was discovered by chance whenAlexander Fleming observed a yellowish mold grow-ing on a bacterial culture in his lab. It was 1928, andFleming had been studying staphylococcus, which isa common bacterium on skin. He noticed that wher-ever the mold grew, an area of clear liquid surround-ing it was free of bacteria. Wherever Fleming spreadthe mold juice, which Fleming called penicillin, bac-terial growth was stopped dead. Although penicillinworked wonders, Fleming was unable to present it tothe public. Apparently people were not ready to ac-cept a microorganism that could make an effective an-tibiotic.

Twelve years later, a young Australian doctor namedHoward Walter Florey, along with his colleagues ErnstBoris Chain and Dr. Norman G. Heatley, showed theworld that penicillin was indeed a miracle drug. Itkilled the bacteria that caused scarlet fever, pneumo-nia, diphtheria, and meningitis, as well as other com-mon bacterial infections.

The discovery of penicillin was so important thatAmerican soldiers were sent to collect soil samples fromIndia, China, Africa, and South America so that it couldbe tested for other miracle molds. Employees of theU.S. Department of Agriculture laboratory in Peoria,Illinois, were instructed to collect any unusual moldsas well. One employee, Mary Hunt, earned the nick-name Moldy Mary because she searched through peo-


ple’s garbage cans and litter. While poking through aneighbor’s trash, Mary found a rotting cantaloupe thathad a golden mold growing on it. When the melonmold was tested, it produced twice as much penicillinas Fleming’s mold, and it grew easily in large quanti-ties. It was named Penicillium chrysogenum, and it re-placed Fleming’s mold for use in penicillin productionuntil researchers learned to make the drug synthetically.

Drugs Dug from the EarthEvery pharmaceutical company raced to find new an-tibiotic compounds. Bristol-Meyers Pharmaceuticals


sent envelopes to all of its stockholders with instruc-tions to collect soil samples from their neighborhoods.Other companies contacted missionaries in far-offplaces, foreign news correspondents, airline pilots, anddeep-sea divers in their search for a mold that mightlead to a new treatment.

In 1943 Dr. Paul Burkholder at Yale University sentout plastic mailing tubes to everyone he knew and re-ceived more than seven thousand soil samples in re-turn. One soil sample sent from Venezuela containeda powerful antibiotic that was eventually developedinto the drug called Chloromycetin. It killed manydifferent kinds of microbes, including the deadly bac-teria that caused Rocky Mountain spotted fever andtyphus.


In the wake ofAlexander Fleming’sdiscovery of penicillinin 1928, the U.S.Department ofAgriculture discoveredthat mold growing onrotting fruit produceslarge amounts of theantibiotic.

Dr. Selman Waksman at Rutgers University workedfor the pharmaceutical firm Merck & Company. Hetested the mold found in the throat of a New Jerseychicken. It contained a compound called streptomycinthat killed the tuberculosis bacillus—something peni-cillin could not do.

Man over MicrobesWith the development of antibiotics, common infec-tious diseases lost their grip on the world. People be-lieved that man had conquered harmful bacteria andviruses. The medical community even fulfilled Jenner’sprediction of annihilating smallpox.

By the end of the 1800s, many European countrieshad enacted laws requiring its citizens to be vaccinatedagainst smallpox. In short order, the virus disappearedfrom many countries. Surprisingly one of the lastWestern countries to eradicate smallpox from withinits borders was the United States, in the late 1940s.

The success of mandatory vaccination inspired officialsat the United Nations to adopt a resolution to eradicatesmallpox from the forty-four countries that still reportedits occurrence. The World Health Organization (WHO),which is part of the United Nations, set a deadline ofJanuary 1, 1977.

Teams of medical workers searched for outbreaks ofsmallpox in poor pockets of major cities and remotevillages. Wherever an outbreak occurred, the teamswooped in to vaccinate all the inhabitants, creating aring of containment around the victims in a particulararea. Those who were infected were put into quaran-tine. Defusing each epidemic case by case and countryby country, the WHO successfully snuffed out the onceraging flames of smallpox.

By 1979 the WHO declared the project a success. Theonly places on Earth where smallpox existed were inlaboratory test tubes. One question remained: Whatshould be done with the stored virus? Some nationsvoluntarily destroyed their supplies, and others handedthem over to research centers in the Soviet Union or


the United States. There are now about four hundredvials of frozen virus securely stored at the U.S. Centersfor Disease Control in Atlanta, Georgia, and anothertwo hundred stored in a lab in Moscow. Although theWHO ordered the destruction of all smallpox samplesin 1993, the order was not carried out. Scientists stilldebate the validity of destroying a virus species. Someargue that more study could provide clues to fightingother deadly microbes.


A Nigerian womanreceives a smallpoxvaccination in 1969during the WorldHealth Organization’seffort to wipe outsmallpox. By 1979the virus had beeneradicated.

Fighting BackThe elimination of smallpox and the availability of somany antibiotics lulled the world into believing thatinfectious diseases were a thing of the past. The U.S.surgeon general William H. Steward even declared be-fore Congress in 1969 that he was ready to “close thebook”17 on infectious disease. The development of an-tibiotics was put on the back burner.

But as quickly as man could manufacture antibioticsand vaccines, bacteria and viruses were faster to developresistance to the drugs. In an interview with Newsweek,Dr. Richard Wenzel of the University of Iowa said, “Eversince 1928, when Alexander Fleming discovered peni-cillin, man and microbe have been in a footrace. Rightnow the microorganisms are winning. They’re so mucholder than we are . . . and wiser.”18

Microbes MutateThe wisdom of a microbe lies in its ability to change.They are able to reproduce much faster than their hu-man competitors. A new generation can come along asquickly as every fifteen minutes, and each time a bac-terium divides, there is a chance for error. A randomchange in the genetic makeup of a cell that becomes apermanent inherited characteristic is called a mutation.And a mutation that increases a microbe’s chance ofsurvival is passed on to the next generation.

Bacteria can also trade or share parts of their DNAthrough a process called horizontal gene transfer. In ad-dition to strands of DNA, bacteria have rings of DNAcalled plasmids. These plasmids give the bacteria cer-tain survival skills, such as being resistant to a type ofantibiotic. This means that bacteria in the same gener-ation can potentially share advantageous plasmids, justas easily as two friends exchange phone numbers. Twobacteria can exchange a gene or genes that allow themto inhabit a new species of animal, thrive in a new cli-mate, or protect them against a certain drug.


Growing ResistanceThe use of antibiotics creates a situation in which thefittest microbes survive. Each time someone uses anantibiotic, the majority of the bacteria are killed butnot all. These heartier microbes are left to multiplyand spread their resistance to the next generation.Within four years of the widespread use of penicillinin the 1940s, doctors saw evidence of microbes thathad grown resistant to it. Even Alexander Fleminghimself warned the public in a New York Times inter-view of the dangers of taking antibiotics. “The mi-crobes are educated to resist penicillin and a host ofpenicillin-fast [resistant] organisms is bred out whichcan be passed to other individuals and from them toothers until they reach someone who gets a septicemiaor a pneumonia which penicillin cannot save.” 19

As each new antibiotic came on the market, a mi-crobe came along that could withstand the toxic ef-fects. Today doctors are encouraged to stop prescrib-ing antibiotics for viral infections, because they haveno power over a virus. And when patients are pre-scribed an antibiotic, they need to take the entire dose.After two days on an antibiotic, a patient usually startsto feel better, but that is only because the antibiotichas killed off a significant number of bacteria. Theminute treatment is stopped, the surviving bacteriabegin to multiply. It takes only one drug-resistant bac-terium to multiply into millions.

The Bacteria EatersOne treatment that may prove to be a solution to theproblem of antibiotic resistance comes from an un-likely source—viruses. It is a method developed inRussia before Fleming discovered penicillin. To mod-ern mentality it seems bizarre, for it pits microbesagainst each other.

Phage therapy harnesses specific kinds of virusesthat attack only certain harmful bacteria. Discoveredand named by Felix d’Herelle in 1917, bacteriophages(bacteria-eating viruses) were soon used by doctors to


cure cholera and typhoid fever. Although the treat-ment never caught on in the West, research contin-ues, particularly in the Republic of Georgia. Today theworld’s foremost center for the development of phagetherapy is at the Eliava Institute in Tbilisi, Georgia.Doctors at the institute study a wide range of virusescollected from nature. The viruses that are activeagainst harmful bacteria are then cultivated and usedfor treatment. A patient suffering from an antibiotic-resistant bacterial infection is injected with a solutionthat contains the proper bacteriophages. The virusesseek out the larger harmful bacteria and inject theirgenetic material into the cell, where it hijacks the bac-teria’s reproductive machinery. Only one hundred bac-teriophages placed on an infected wound is enoughto destroy more than 100 million bacteria. Once thebacteria are eliminated, the viruses also die out. Theyhave no cells to infect and are washed harmlessly outof the patient’s body.

More than twenty companies in the United States arenow studying and testing phage therapy in the lab andwill seek future government approval to conduct clini-cal trials on humans. In the meantime, dozens of ex-otic, mysterious illnesses are cropping up all over theworld.

Staphylococcusbacteria are destroyedby antibiotics.Although antibioticsare extremely effective,their use over timeresults in heartier,drug-resistant strainsof bacteria.

EmergingMicrobes

54

Chapter 4

Many infectious diseases, like smallpox, polio, andanthrax, are ancient and have plagued humankind

for thousands of years. But new strains of bacteria andviruses continue to emerge seemingly out of nowhereto cause mysterious new ailments.

In Wisconsin in May 2003, three-year-old SchyanKautzer came down with symptoms vaguely reminis-cent of smallpox. Eileen Whitmarsh, a forty-two-year-old pet store owner, developed flulike symptoms alongwith blisters on her head and under her arms. Two em-ployees at a veterinary clinic also became sick. The onething they all had in common was a close encounterwith prairie dogs. The three-year-old had received a prairiedog for a pet, the pet store owner had had the animalsin stock, and the workers at the clinic had recently treateda sick prairie dog.

Blood samples taken from all the victims revealedstartling news: They had a disease never encounteredbefore in the Western Hemisphere—a virus called mon-keypox, a less severe cousin to smallpox. At one timethe virus infected only rodents in Africa, but it hadjumped species and was now known to have infectedfewer than one hundred people in Africa. But how didit travel five thousand miles across an ocean to a smalltown in Wisconsin?

A Global VillageMicrobes are opportunists. They take advantage of likelyand unlikely hosts. The virus that was carried to theUnited States inside an African rodent seized the op-portunity to inhabit a new species when the animal washoused in a small, tightly packed cage next to prairiedogs in a pet store warehouse. The virus mutated, orchanged its genetic code, so that it was able to infect anew species. From a Gambian rat to an American prairiedog, it then jumped to a little girl.

Emerging Microbes 55

Crowded cities andthe ease ofintercontinental travelfacilitate the spread ofmicrobes throughoutthe world.

Humans live in a global society, and our actions af-fect the microscopic community around us. “We dothings as part of progress, which we don’t recognize aschanging the microbial environment,”20 says G. RichardOlds, the chairman of medicine at the Medical Collegeof Wisconsin and the former head of the TropicalDisease and Travel Medicine Center in New England.Everything a person does affects the microscopic world:traveling in airplanes, eating foreign foods, and livingin crowded cities. As Olds says, “Nothing happens onthis planet that doesn’t impact us. We’re wearingclothes that were made in China. We’re eating foodsthat were grown in Chile.” 21 Infective agents cancome from anywhere, and frequently do. Monkeypoxappeared in this country because of people’s passionfor exotic pets.

But the connection between man and microbe wasnot always so apparent. Disease was something thatjust happened to a person, and there was little thoughtas to why or how a person’s behavior or activities con-tributed to their illness. It took hundreds of years be-fore someone thought to look at our own behaviorand modify it in an attempt to prevent the spread ofdisease.

The First Disease DetectiveIn 1854, during the Industrial Revolution, living con-ditions in many parts of urban England were poor.Factories belched black smoke, and slums were over-crowded and unsanitary—the perfect conditions forbacteria and viruses. An outbreak of cholera occurredin a small area near Broad Street in London. Cholerais contracted by drinking water infected with thecholera bacterium or eating food contaminated by it.Cholera causes severe diarrhea, vomiting, fever, anddeath.

When physician John Snow began questioning peo-ple in the neighborhood, he noticed that of the seventy-seven households infected with cholera, fifty-nine used


the hand pump on Broad Street. Families that remainedhealthy used a water pump farther away.

Near the Broad Street well was a cesspool that con-tained the waste and garbage of the neighborhood.Snow believed that sewage from the cesspool had con-taminated the drinking water. He begged the board oftrustees of the St. James Parish to remove the handlefrom the pump to prevent people from collecting thecontaminated water. Although no other physicianagreed with Snow’s assessment, the men on the boarddid as he advised. The handle was removed and thecases of cholera declined. Later Snow learned that thebricks lining the cesspool were indeed old and broken,and sewage had leaked into the well.

Disease Detectives TodayThe same kind of detective work that Snow con-ducted in the 1800s is carried out today by scientistsat the Centers for Disease Control and Prevention(CDC) headquartered in Atlanta, Georgia, and theDivision for Emerging and Other CommunicableDiseases Surveillance and Control at the WorldHealth Organization (WHO). More properly calledepidemiologists, these scientists study the spread ofinfectious illnesses and respond to outbreaks any-where in the world.

They watch for the emergence of a new disease oran old microbial adversary using a network of doctorsand high-tech equipment like satellites and theInternet. The WHO is continuously monitoring theWorld Wide Web with a customized search enginecalled the Global Public Health Intelligence Network,listening for rumors and reports of suspicious disease-related events. Online eavesdropping led to the earlydetection of the 2003 outbreak of SARS (severe acuterespiratory syndrome).

When a suspicious event is detected or when epi-demiologists are consulted by local authorities, these sci-entists use some of the same skills that police detectives


use when trying to solve a crime. They interview the pa-tients, their friends, and family to pinpoint the initialsigns of illness. They ask patients what they may haveeaten, what animals or animal products they may havecome in contact with, and where they may have trav-eled. As each person is interviewed, patterns of the dis-ease emerge. Are the victims all children, or are they alladults? Are they mostly male or female? Knowing whenan outbreak began, who it affected, and when it endedgives epidemiologists an idea of the kind of disease thatcould have occurred within that time frame.

Epidemiologists also track each patient’s activities tonarrow down the possible source of infection and ploteach incident on a map to see if there is a geographi-cal element. They search the area for evidence of ani-mal activity, insects, or contaminated water or food.Doctors take samples of blood or tissue and send themto their lab in Georgia, where microbiologists will iden-tify the microbes involved in the incident.


Epidemiologists fromthe World HealthOrganization conductresearch on the Ebolavirus. Epidemiologistsstudy the incidence,spread, and control ofinfectious diseases.

Suspect infectious agents are examined in a labcalled a biocontainment unit. There are four levels ofsecurity and safety features in the labs. The mostdeadly infectious agents are examined in biocontain-ment unit level 4, which is as airtight as a space shut-tle. Air locks and a ventilation system that sucks airinward prevent dangerous bacteria or viruses fromdrifting out. Microbiologists suit up in astronaut-like“blue suits” complete with their own air supply. Atthe end of the day, the workers are decontaminatedin chemical showers. The evidence found in the labcombined with the information gathered in the fieldwill lead to the cause and hopefully the treatment ofthe infection.

Microbes on the MoveEpidemiologists respond to outbreaks all around theworld, but today our world is more mobile than everbefore, and that mobility means that microbes are onthe move too. “One of the most important means ofspreading diseases around the globe is air travel,” 22

says David Heymann, the director of communicablediseases for the World Health Organization.

Every day, more than 500 million people travelacross international borders, and tens of billions ofbacteria and viruses hitch a ride. In 2003, within sixmonths of the first reported case of SARS in China,the disease was spread by air travel to twenty-sevenother countries. All the victims who came down withSARS in Toronto, Canada, could be traced directly backto one woman who had traveled from Hong Kong.And shortly after the Toronto outbreak, the WorldHealth Organization warned travelers not to visit thecity and effectively prevented the virus from spread-ing further.

Changing the EnvironmentPeople not only get around faster than ever before,but they change the environment more easily too.


Every day, in some part of the world, whole tracts ofrain forests are bulldozed, rivers are dammed, and newroads are paved into the wilderness. This disrupts thebalance and distribution of plants and animals, in-cluding microbes. It may cut off a virus from its hostso that the virus must seek another means of survival.

The story of Lyme disease, which causes arthritis-likeaches and pains, provides an example of this process.In the 1800s settlers in Old Lyme, Connecticut, clear-cut the old growth forests, which led to a decline inthe deer population. A hundred years later, when theagricultural production in that area ceased, the forestsreturned, along with a burgeoning deer population.But the human population grew too. Housing devel-opments in forested areas put man, deer, and microbeson a collision course.

The spirochete Borrelia burgdorferi is passed from adeer to a deer mouse by the bite of an infected deer tick.The deer and the deer mouse do not seem particularlyaffected by the microbe, but people are. When peoplestarted to build houses in Old Lyme, they unwittinglyplaced themselves in the path of the microbe and addeda new host to the microbe’s list.

Even making more subtle changes to the landscape—such as digging pools, opening irrigation ditches, anddiscarding tires—create new niches for vectors, animalsthat are capable of carrying human disease. Insectscarry about one hundred different human diseases,which are called arboviruses (arthropod-borne viruses).Topping the list are yellow fever, dengue fever, malaria,and West Nile virus.

West Nile VirusIn the summer of 1999 the New York City Health Depart-ment battled a mysterious outbreak of encephalitis(inflammation of the brain) among a group of elderlypeople living near LaGuardia Airport. Tests revealedthat it was West Nile virus, a disease never before seenoutside of the Middle East.


The virus is carried by mosquitoes that take advantageof hot, wet summers in urban and suburban areas. “WestNile is extraordinarily good at adapting to this new en-vironment,”23 said Ian Lipkin, director of the Jerome L.and Dawn Greene Infectious Disease Laboratory atColumbia University. Mosquitoes lay infected eggs inpuddles, pools, overturned toys, garbage cans, and anyother place rainwater can accumulate.

West Nile usually infects birds. People living in thesuburbs of Chicago, one of the most heavily hit areas,reported an eerie silence where once songbirds trilledand crows cawed. No one knows why or how it got tothe United States, but this versatile virus managed toquickly jump species once it arrived. It is now knownto infect dozens of bird species, as well as humans,horses, chipmunks, squirrels, raccoons, bats, rare rhi-noceroses in zoos, and wild alligators. These animalsare only innocent bystanders in the virus’s life cycle.

In order to cause disease, a mosquito must first bitean infected bird and pick up the virus, which ends upin the digestive tract of the mosquito, where it multi-plies. While other arboviruses are carried inside the gutof only one or two species of insect, the West Nile virushas been found living in thirty-six different species ofmosquito. The virus spreads throughout the mosquito’sbody, ending up in the salivary glands. When the mos-quito bites its next victim, the virus is injected into thenew host along with mosquito saliva.

Deer ticks like thisone can carry Lymedisease, a viralinfection that causesarthritis-like achesand pains.

In the short time since West Nile virus first appeared,scientists have learned a great deal about it. The virus’sability to replicate is closely related to the weather. At70 degrees Fahrenheit, it takes the virus three weeks tomultiply to a point where it is transferable to anotheranimal. At 80 degrees Fahrenheit, the time is shortenedto two weeks, and during spells with temperatures higherthan 90 degrees Fahrenheit, it takes only one week. Thehotter the weather, the more infectious the disease be-comes. This information is not just interesting virustrivia; it is vital data that allows health officials to pre-dict the severity of an outbreak by monitoring theweather. If a large outbreak is predicted, then officialsmay spray insecticides and issue health warnings to res-idents in the area. But even with early warnings, the dis-


West Nile Transmission

ease is spreading. At the end of 1999, the CDC reportedthat sixty-two people had been infected in four statesand seven people had died. Within three years, the virushad spread to forty-four states, reporting 4,156 cases ofillness and 284 deaths.

Hidden DangerSome infectious diseases are spread by animals, whileothers are passed directly from person to person. Somemay sweep through a population like wildfire, whileothers lurk and linger.

In the summer of 1981, five men in Los Angeles werehospitalized with weakened immune systems and un-controlled rare infections and tumors. Not long after-ward, similar cases were reported in New York, SanFrancisco, and Newark, New Jersey. By the end of theyear, 150 cases of the illness had been reported andthirty people were dead. This was the first slow ap-pearance of what would later be called human im-munodeficiency virus (HIV), which causes AIDS (ac-quired immunodeficiency syndrome). After years ofstudy, researchers discovered that this RNA retrovirusmight have made its first appearance in the human pop-ulation as early as 1959, perhaps even earlier. HIV is ca-pable of hiding out within a person’s cells for up totwenty years before the symptoms of AIDS develop.Like other viruses, HIV targets one particular kind ofcell, but the reason that HIV is so deadly is that it at-tacks the immune system’s white blood cells. By enter-ing and killing only those cells, the virus kills the cellsthat allow the body to protect itself against other in-fectious diseases.

Hiding out inside a person’s cells for years is an ef-fective way for the virus to survive. It can be passedfrom person to person long before any signs of illnessappear. HIV can spread through having contact withblood and other bodily fluids from an infected per-son, engaging in sexual activity with an infected per-son, sharing a contaminated hypodermic needle, and


receiving a blood transfusion. It may also be passedfrom an infected mother to her fetus during pregnancy.

As one of the smallest viruses, measuring only .1 mi-cron in size, HIV has caused as much devastation in theAfrican continent as smallpox did in the New World fivehundred years ago. In Zimbabwe and other Africancountries, one out of every five adults is infected. Butthe virus is also a worldwide epidemic. The WHO re-ported that at the end of 2003 an estimated 40 millionpeople across the globe lived with HIV, and the diseaseAIDS had taken the lives of 25 million. With no vaccineand very few effective long-term treatments, AIDS con-tinues to take the lives of 3 million people every year.

Biological Warfare and TerrorismIt would seem that the CDC and the WHO haveenough on their plate just monitoring and respondingto natural outbreaks of disease, but they also respondto acts of bioterrorism—the use of a biological substancelike a bacteria or a virus as a weapon. Bioterrorism is aconcept nearly as old as war itself. Greek and Romanarmies threw dead and bloating animals into their en-emy’s water supplies to make them sick. In 1763 British


An electronmicrograph shows a T cell infected withthe HIV virus. Thevirus can lie dormantin the human bodyfor years before itdevelops into AIDS.

officers gave gifts of smallpox-infected blankets to un-suspecting Native American chiefs. For decades manynations, including the United States, experimented withmicrobes as weapons until the ratification of theBacteriological and Toxic Weapons Convention in 1972.But evidence suggests that some countries and terror-ist groups still have active biological warfare programs.

The list of potential bacterial and viral weapons isshort but deadly. The microbes most likely to be usedfor an attack are those that are highly lethal, easilyproduced in large quantities, and easily transmittable.Anthrax tops the list, because it can be collected fromsoil samples or illegally acquired from germ banks. Itcan be contracted through the skin or ingested. It at-tacks the body and shuts down the immune system.Inhaling anthrax is almost always fatal.

Each year the U.S. federal government responds to hun-dreds of anthrax hoaxes, but on October 5, 2001, it wasthe real thing. On that day began a series of biological


FBI agents work todecontaminate aFlorida buildingtargeted during theanthrax terroristattacks of October2001.

terrorist attacks in which envelopes containing high-gradeanthrax were sent to addresses in Florida, New Jersey, NewYork, and Washington, D.C. Seventeen people were takenill, and five people died. The attacks shut down the postalservice and other government agencies for several days,costing the nation millions of dollars.

The botulin bacterium has also been used as a weaponbecause it produces one of the most toxic chemicalsknown, but it cannot be as effectively distributed. In1984 members of the Rajneesh cult in Oregon sprinkledthe bacteria on restaurant salad bars in an attempt to af-fect the outcome of an upcoming local election. TheOregon incident injured more than seven hundred cit-izens but did not cause any fatalities.

The smallpox virus is another cause for concern.When the virus was eradicated from nature, there wasno need to continue the vaccination program, so to-day very few people have a natural immunity to fightthe disease. It would spread easily through a popula-tion. In 2002, in the wake of the World Trade Centerattack and the anthrax incidents, President George W.Bush announced reinstating a voluntary smallpox vac-cination program for frontline health-care workersand first responders and a mandatory vaccination pro-gram for military personnel.

Investigations have uncovered that microbes likesmallpox or anthrax can be obtained illegally from un-regulated labs and former storehouses. No one knowshow many deadly germs are available or easily obtain-able, but according to the World Federation for CultureCollections, there are forty-six registered germ banksthat contain anthrax, and there are more than onethousand that are not registered or regulated.

These germ banks are like microbial libraries wherelegitimate scientists can request specimens of certainbacteria or viruses for research purposes. They holdmore than just dangerous pathogens. Germ banks alsocontain an assortment of other bacteria and virus cul-tures that are experimented with and used for more pos-itive purposes.


HarnessingInvisible Power

67

Chapter 5

For centuries people have been using microbes totheir advantage, turning grapes into wine, milk

into cheese, and cabbage into sauerkraut. People ben-efit from what microbes do naturally: They eat. Theydigest organic compounds, changing the chemicalmakeup of one product and turning it into a com-pletely different yet tasty food or drink.

Milk, for example, is turned into cottage cheese whenthe bacteria Leuconostoc break down the milk sugar (lac-tose) to produce lactic acid. The acid curdles the milkinto cheese curds. Different types of bacteria or moldmake different kinds of cheeses.

Bacteria are used in the production of all kinds offoods. Before coffee beans are washed, dried, androasted, they are first soaked in a tank of bacteria thatbreak down bits of shell still stuck on the bean. Andwithout microbes, there would be no chocolate. Cocoabeans must first be fermented by bacteria and yeast be-fore they become edible.

Louis Pasteur described the fermentation processmore than one hundred years ago as the addition of aliving organism such as a bacteria or yeast to anothersubstance. Under anaerobic conditions (where no oxy-gen is present), the bacteria break down the carbohy-drates and produce alcohol and carbon dioxide. For cen-turies this process has resulted in wine, beer, bread, andother good things to eat.

Genetic EngineeringToday, in order to get bacteria to produce a desired prod-uct, they are first altered through a process called ge-netic engineering. Bacteria are useful because theirstrands of DNA float loosely in the cell, making themeasy to get at. They also have several plasmid rings thatgive a cell resistance to certain chemicals and determinewhat kind of materials it can break down and use forfood or what enzymes it can make. Once a gene is iden-tified, it can be taken out and inserted into another bac-terium.

Genetic engineers have devised two ways to insert ge-netic information into a cell. One way is to use an RNAretrovirus as a vector. Just as an animal or insect vectorcarries a disease from person to person, a virus can beused to carry genes from one cell to another.

First the scientists must remove any harmful parts ofthe virus so that it will not cause disease. The desiredgene or genes are then inserted inside the virus. Whenthe virus infects the appropriate cell, the cell copies thevirus’s RNA, incorporating the bits of genetic informa-tion into its own DNA. Virus vectors are used to mod-ify plants and are being experimented with for use ingene therapy for genetic disorders.

But the tool that is most commonly used in indus-trial genetic engineering is the bacterial plasmid, whichis used to insert new genes the same way that bacteriaexchange genetic information naturally. Special en-zymes cut the plasmid at specific locations, opening upthe DNA at precise points. A gene is taken out and re-placed by a new gene that will give the bacteria the de-sired characteristic. It is inserted back into the plasmidand “glued” in place with another enzyme. The engi-neered plasmid is then reinserted back into the bac-terium.

Each time the bacterium divides, the engineered plas-mid is duplicated as well. When trillions of these bac-teria contain the altered genes, they become powerfulminifactories producing much-needed products.


Microbial FactoriesEngineered microbes are a cheap labor force. They do nottake up much space or eat a lot. Massive quantities of bac-teria can be grown in bioreactors—enormous stainless-steel vats several stories high, filled with a nutrient-rich substance to keep the bacteria productive. In thiskind of environment bacteria churn out acids, proteins,and enzymes that are used to manufacture a wholehost of products.

Using engineered microbes in an industrial settingis called bioprocessing. The first step is finding the ap-propriate microbe for the job and the perfect livingconditions for the microbe’s maximum production. Aslight change in the temperature, concentration of nu-trients, or level of oxygen inside the vat may dimin-ish the bacteria’s productivity.

One of the first uses of microbes in industry was themanufacture of vitamins that are added to foods ormade into supplements. Many vitamins can be syn-thesized or made by combining certain chemicals in

A pharmaceuticaltechnician works witha bioreactor.Bioreactors housemillions of engineeredmicrobes that producethe basic buildingblocks of a widevariety of products.

a lab, but others have far more complicated molecu-lar structures. Humans normally depend on microbesto manufacture these vitamins for them as they digestfood in the intestines. In the manufacturing world, bac-teria are also depended on to create these essential com-pounds. The bacterium Bacillus subtilis is used to pro-duce the much-needed vitamin called riboflavin, whichis used by all living cells to create certain proteins. Thebacterium secretes the riboflavin through its cell mem-brane. Once free of the bacteria, the riboflavin must beseparated from the growth medium. This can be doneby spinning it in a centrifuge or distilling it out.Manufactured riboflavin is added to cereals, bread, andother fortified foods.

The bacterium Lactobacillus bulgaricus makes lacticacid, which is used not only to preserve and fermentfoods but also to dissolve lacquers on furniture and re-move hair from cowhides before they are tanned intoleather. Aspergillus niger produces vast quantities of cit-ric acid, which is used in soft drinks, candies, inks, andAlka-Seltzer. The Bacillus subtilis bacterium is also ge-netically altered to produce protease, an enzyme thatis added to meat tenderizers, drain cleaners, liquid glue,and laundry detergent.

High-fructose corn syrup that sweetens most softdrinks is also made with bacteria. Cornstarch is treatedwith a series of three enzymes to convert its sucroseinto fructose, which is twice as sweet and thereforecheaper to use. The enzymes used in the process aremade by bacteria.

By genetically altering a bacterium’s DNA and in-serting a human gene, scientists can program a bac-terium to produce a human protein. The gene for mak-ing human insulin, for example, is inserted into thebacterium’s chromosomes so that it begins to churnout vast amounts of insulin that is needed by peoplewho suffer from diabetes. Other strains of bacteria havebeen programmed to make human growth hormoneand a vaccine for hoof-and-mouth disease. Every day,


researchers work on ways that bacterium can manu-facture more drugs and hormones to treat other med-ical problems.

Feeding the WorldGenetically altered bacteria and viruses are also used inagriculture. Originally, genetic engineering techniquesworked well only with animal cells, because plants havetough cell walls that most bacteria can not get through. Andthose that can are usually harmful. But scientists founda way to take a harmful bacterium called Agrobacteriumtumifaciens, which normally causes crown gall disease,and make it beneficial. The bacterium infects a plant byinserting its DNA into the plant cell, which causes a tu-mor to grow. But when the disease-causing gene issnipped out of the bacterium’s plasmid, the bacterium isrendered harmless and becomes the perfect vector.

Viruses can also be used to modify plant genes. Onesuch virus comes from the well-studied mosaic virusfamily, namely the cauliflower mosaic virus. It can berendered harmless and fitted with genetic informationthat makes a plant more tolerant to herbicide or moreinsect resistant.

Genetically engineered foods are already on the mar-ket. Scientists have developed tomatoes that keep theirfresh taste longer, peas that retain their sweetness, andstrains of corn and wheat that are pest resistant. Somegenetically modified potatoes contain 60 percent morestarch. The extra starch decreases the amount of cook-ing oil that soaks into the potatoes, solving the problemof oily potato chips or greasy french fries. But more col-orful tomatoes or greaseless chips are not the only rea-sons for this growing field of science.

Some scientists believe that genetically modified foodsmay be an important tool for feeding the world in thefuture. Researchers predict that we will need to increaseglobal food production by 50 percent within the nextfifty years in order to keep up with the populationgrowth. That is a tall order to fill. So genetic engineers

Harnessing Invisible Power 71

are looking at ways to increase production; for example,developing plants that produce more food than theynormally would or are able to fight off diseases thatwould otherwise diminish their yield.

But other scientists argue that genetically modifiedfoods and plants are a cause for concern. They debatethe safety and long-term effect that consuming mod-ified foods will have on a person’s health and the pos-sible consequences of releasing genetically engineeredrecombinations into the environment. Mutations thatmay occur naturally within a plant will still occurwithin genetically modified cells. There is also the po-tential for naturally occurring viruses to recombinewith the genetically altered viral DNA inserted into theplant. Could this cause a more virulent infection some-time in the future? As the debate continues, more thanhalf of all food for sale in North America contains someform of genetically modified ingredients.

BiominingThe food and drug manufacturers are not the only in-dustries that have used bacteria successfully. Anotheris the mining industry, which uses microbes to extractminerals from poor deposits of ore, a process dubbedbiomining. The copper industry was the first to take

Genetically alteredbacteria and virusesare used to createdisease-resistantplants that producemore food thanunmodified plants.

advantage of these mini-miners. The bacterium Thio-bacillus ferooxidans gets its energy by metabolizing in-organic materials. As the bacteria eat, they release awaste product of acid and an oxidizing solution of fer-ric ions. Together these wash the metal right out ofthe ore. The Romans first described this natural processtwo thousand years ago when they noticed that therunoff from a pile of leftover ore was blue with cop-per salts. The ancient miners found a way to recoverthe copper without ever knowing how it got there.The bacterium responsible for this phenomenon wasnot discovered until the 1960s. Today T. ferooxidans isused to extract more than 25 percent of all the cop-per mined in the world from what was once consid-ered low-grade ore.

Gold ore, once thought to be useless for mining, isalso releasing its gold deposits with the help of T. fero-oxidans. A brew of microbes and fertilizer can bepoured directly onto piles of crude ore. This method


Miners use microbesto extract mineralsfrom poor deposits ofore, a process knownas biomining.

is much cheaper, more efficient, and more environ-mentally friendly than other extraction processes.

So far the bacteria used in mining are collected frommining areas where they occur naturally. Because bio-mining has become so lucrative, the next step is to cre-ate super–mining microbes through genetic engineer-ing to make them more efficient in the mining field.Once created, they could be mixed with microbes thatcan, for example, withstand extreme heat or resist toxicchemicals such as arsenic and mercury, which are usedin processing gold.

There are so many different kinds of bacteria withso many different behaviors that scientists are alwayson the lookout for bacteria with unusual appetites andattributes. If one kind of bacteria can release gold fromrock or turn sugar into alcohol, then perhaps anothercan turn wastewater into clean water.

Clean WaterThe people of New York City produce 1.4 billion gallonsof wastewater every day. Part of that—between 125 and340 million gallons—is cleaned at the North Riverwastewater treatment plant on the Hudson River, whichtakes the sewage from Manhattan and cleans it withthe help of bacteria. The wastewater is pumped into fivethirty-foot-deep airing tanks that stimulate the growthof oxygen-loving bacteria. These microbes consumemost of the organic materials or sludge in the waste-water. Then oxygen-hating (anaerobic) bacteria are usedto clean the remaining sludge. In tanks called digesters,the sludge is heated to 95 degrees Fahrenheit to promotebacterial growth. As the bacteria eat the sludge, they pro-duce methane gas. Instead of venting the methane outinto the atmosphere, the gas is used to heat the digestertanks and run the other machinery at the sewage plant.Nothing is wasted, and the bacteria do most of the work.

The Oil EatersOther microbes are hard at work cleaning oil spills. InMarch 1989, when the Exxon Valdez oil tanker spilled


more than 11 million gallons of crude oil, it contami-nated hundreds of miles of shoreline. Cleanup crewsworked furiously to save the wildlife, but in the end,more than a quarter of a million birds, five thousandsea otters, and three hundred harbor seals lost their lives.

Within a few weeks, however, divers discovered thatthe most contaminated area in the ship’s hold wasthriving with sea life. Mother Nature had set out to re-pair herself. Naturally occurring bacteria in the waterresponded to the disaster and grew. They used the oillike food, changing the toxic petroleum into a harm-less substance, a process that occurs only when othernutrients like nitrogen are present. Researchers learnedfrom this discovery. Instead of washing away the oilfrom the shoreline with detergents that were harmfulto the wildlife, they sprayed nitrogen onto the oil toencourage the growth of the oil-eating bacteria.

But cleaning that spill up was nothing compared tocleaning up the five hundred thousand tons of crudeoil released into the water and soil surrounding theMina Al-Ahmadi terminal during the 1990 Persian GulfWar. Newspapers around the world mourned the lossof plant and animal life in the region from the largest

Workers clean rocksafter the 1989 ExxonValdez oil spill.During the cleanup,researchers learnedthat naturallyoccurring bacteriaconvert oil into acompletely harmlesssubstance.

oil spill in history. Two years later, however, large matsof blue-green algae, or cyanobacteria, were growing ontop of the oil-soaked soil. Embedded in the mats ofcyanobacteria were millions of other bacteria, busy eat-ing the oil and breaking it down into carbon and en-ergy.

Researchers found a way to simulate these mats ofmicrobes by using powdered clay sprinkled on the oil.The clay floated on the surface of the water and ab-sorbed the oil, creating little islands where bacteria couldfloat and feed. In one experiment, bacteria broke downthree-quarters of a test spill in less than five weeks, aprocess that in nature would have taken closer to fiftyyears.

BioremediationIn 1975 a massive leak at a military storage facilityspilled eighty thousand gallons of kerosene-basedjet fuel outside a quiet suburb of Charleston, SouthCarolina. Although the cleanup effort contained thespill, it could not prevent the fuel from seeping intogroundwater. In less than ten years, highly toxic chemi-cals, such as cancer-causing benzene, had reached resi-dential neighborhoods.

Studies conducted by the U.S. Geological Survey (USGS)found that microorganisms in the soil were activelyconsuming the toxic compounds. As they ate, theytransformed the compounds into harmless carbon diox-ide. By stimulating the bacteria with nutrients, the USGSteam found they could increase the bacteria’s activity.Through specially made infiltration systems, the nu-trients were pumped into the contaminated soil. Taintedgroundwater was filtered out and cleaned. In one yearthe contamination was reduced by 75 percent.

The process of using microbes as miniature cleanupcrews is now called bioremediation, and it is big busi-ness. More than fifty bioremediation companies usemicrobes to clean the soil at former industrial plants,military ammunitions sites, and old gasoline stations.


Gasoline is the most common contaminant ofgroundwater throughout the United States. Thousandsof steel tanks buried beneath old gas stations are cor-roding and leaking gas into the soil. “These tanks areeverywhere; it’s a nationwide problem,”24 says LoringNies, an assistant professor of environmental engineer-ing at Purdue University. Before microbes were used, thesoil had to be completely removed down to depths ofseveral feet—an expensive and labor-intensive process.


Rusty barrelscontaining toxicmaterials can releasetoxins into the soil.Using microbes toclean up such wastehas become acommon practice.

Now microbes that occur naturally in the soil are “fed”by pumping phosphorus and nitrogen into the ground,promoting rapid bacterial growth.

Another type of bacteria that likes to eat poison iscleaning up old contaminated mining sites. Gold is tra-ditionally separated from ore using cyanide, a highlytoxic substance that can kill within minutes if ingested.After processing, the cyanide is washed away and endsup in nearby streams and creeks. The Homestake Minein South Dakota, the largest gold mine in North America,had been washing cyanide into Whitewood Creek formore than a hundred years. The creek was so pollutedthat it was thought to be sterile: Nothing could live in it.But when researchers tested the creek water, they foundthat one type of bacteria was thriving. That bacteriumused the poisonous cyanide as its main food source. Nowthat bacterium is being used to clean up other miningsites as well.

Researchers around the world search for bacteria withuseful appetites. Some, like the mining microbes, arefound in nature, while others are discovered in an end-less array of laboratory tests. At the University of WestFlorida scientists tested more than twenty thousandmutant strains of bacteria before they found one thatturned a toxic industrial chemical, TCE (trichloroeth-ylene), into a harmless substance. Today bacteria areused to detoxify soil and water polluted by PCBs (poly-chlorinated biphenyls), creosote, DDT, and other tough,toxic compounds.

The USGS estimates that cleaning up existing envi-ronmental contamination in the country would costas much as $1 trillion. With bioremediation the costmay be cut drastically and the cleanup will be lessstressful on the environment. But much of what biore-mediation promises has yet to be realized. Designermicrobes will eventually take the place of naturally oc-curring ones and will be able to do the job faster andmore efficiently. One recent project at the Oak Ridge


National Laboratory in Tennessee involved adding abioluminescent gene to one toxin eater to make it glowso that human cleanup crews could see the bacteria atwork.

Even The Guinness Book of World Records “World’sToughest Bacterium” 25 is being put to work. Dein-coccus radiodurans was discovered in 1956 inside a canof meat that had spoiled despite being sterilized by ra-diation. This amazing bacterium can withstand andactually grow during exposure to 3 million rads ofradiation, which is more than one thousand timesthe amount of radiation needed to kill a human. Thebacterium does become damaged during exposure,but in less than one day, it is able to repair its dam-aged chromosomes. Scientists working with theDepartment of Energy are looking into the possibil-ity of using these microbes, or hybrids of them, toclean up radioactive sites left over from the produc-tion of nuclear weapons.

Microbes and MasterpiecesPerhaps the most astounding use of microbes can befound in the back rooms of major art institutionswhere the microbes’ voracious appetites are being letloose on priceless masterpieces, such as the Conversionand Battle of Saint Efisio by Spinello Aretino. ManyItalian works of art dating back to the fourteenth cen-tury were severely damaged during World War II.Attempts to repair them with glue and harmful clean-ing solvents caused even more damage, and aftersixty years they were thought to be hopelessly unre-pairable.

But in 2003, researchers used microbes for the firsttime to remove the damaging glue. The bacteriumPseudomonas stutzeri was applied to the canvases us-ing damp wool compresses. The bacterium quickly atethe harmful residue, almost magically revealing theoriginal pigments underneath. Within twelve hours,


80 percent of the paintings were clean, and the figureswere recognizable for the first time in many years.

Much of what microbes have been used for is clean-ing up our mistakes: damaged works of art, environ-mental oil spills, and toxic pollution. But what doesthe future hold for man and microbe?


A researcher usesmicrobes to restore anItalian masterpiece toits originalmagnificence.

The Future Undera Microscope

81

Chapter 6

Abacterium was the birthplace of genetic engineer-ing, one of the most revolutionary technologies

in science. And since those first experiments with bac-teria back in the 1960s, hundreds of new medicinesand products have become commonplace. But geneticengineering is only the tip of the microbial iceberg. Tounderstand how microbes work in the world aroundus and how they affect our lives, scientists are record-ing their entire genetic code.

Writing the Book of BacteriaIn 1994 the U.S. Department of Energy (DOE) announcedthe beginning of the Microbial Genome Project. Agenome is the complete set of instructions for mak-ing any organism. It is the “parts list” of the organ-ism’s DNA—the list of letters that represent the basepairs that make up the DNA strand. A single micro-bial genome may contain between 500,000 to 8 mil-lion DNA base pairs; the human genome contains 3billion. Whereas the Human Genome Project tookyears to write the “first draft” of the entire genetic ma-terial inside a person’s cells, most microbes can be se-quenced in a matter of weeks or even days. By the endof 2003, more than one hundred bacteria and viruseshad been sequenced.

But why would the DOE want to know every letterin the long DNA sequence of a microbe? Scientists

want to know because these letters hold the code forthe creation of certain proteins that carry out variousfunctions within the cell. Some genes instruct the pro-duction of certain proteins to make the cell wall, whileothers instruct the cell to manufacture hydrogen or toinfect liver tissue. But just as a parts list of a car’s enginedoes not explain the assembly and function of the car,the genome does not provide information about whatthe parts do. Another project called Genome for Life,an extension of the Microbial Genome Project, is seek-ing to understand the function of the genes that havebeen written down.

According to Daniel W. Drell of the DOE and his col-leagues, “We can now look at how the ‘parts’ come to-gether in ways that challenge basic science and offer con-crete applications in a range of issues affecting, forexample, water quality, environmental remediation, andmedicine.”26 The hope is that microbes will prove to bea source of new genes that can be used to solve problemsthat confront society today. The DOE is most interestedin microbes that can address environmental problems,such as global warming and toxic waste cleanup, or leadto new sources of clean, environmentally friendly energy.

Global WarmingOver the past decades scientists have found that Earth’stemperature is rising more rapidly than expected, andthey predict another rise of 1.5 to 4.5 degrees centi-grade over the next one hundred years. This rise intemperature is due to the increased amount of carbondioxide (CO2) and other greenhouse gases that are re-leased into the atmosphere from industrial processes.They eat away at the ozone layer, which protects theearth from the sun’s harmful rays. Coupled with chang-ing land use and deforestation, these gases have long-term effects on the planet. Increased temperatures canlead to a rise in the ocean’s water levels, which erodescoastlines. It could trigger floods and drastically changeecosystems.


But what if there were microbes that ate excess CO2?In 1991 two Japanese microbiologists who were ex-ploring ways to maintain the atmosphere discovereda bacterium called Synechococcus, which thrives onCO2. The scientists believe that knowing the genomeof CO2-consuming bacteria could lead to the futuredevelopment of huge bioreactors filled with bacteriafeeding off of unwanted CO2 in the atmosphere.

Extreme GenesMany of the microbes that the DOE researchers haveselected for the genome project live in extreme places.“The diversity and range of their environmental adap-tations indicate that microbes long ago ‘solved’ manyproblems for which scientists are still actively seekingsolutions.” 27

For example, the bacterium Methanococcus jannaschiigrows in thermal vents eight thousand feet below theocean off the coast of Baja California. It thrives underhigh pressure and temperatures as hot as 190 degreesFahrenheit. It exists in anaerobic conditions and pro-duces methane gas. M. jannaschii is being studied as a

Scientists hope to usemicrobes to eliminateexcess carbon dioxidein the atmosphereand reverse the effectsof global warming inthe Arctic and otherareas.

working model for the production of methane as auseful, renewable energy source.

When scientists know the code for what makes abacterium operate, they will also know how to controlit. And comparing the genomes of one bacterium toanother will allow scientists to see patterns of functionand predict what other microbes are capable of doing.

So far the genome researchers have been awed bythe amount of previously unidentified genes they haveuncovered from some of these extreme microbes. Morethan half of the genes sequenced in M. jannaschii, forexample, were completely unknown to science. Thismeans that the proteins that the genes instruct the cellto create are also unknown. They offer an amazing newresource to explore. The genome project is bringing tolight a vast menu of genetic ingredients of genes andproteins that can be used to genetically engineer newmicrobes and new products.

The DOE is not the only place that is sequencing thegenes of microbes. Medical institutions focus on thebacteria and viruses that cause disease. If scientists canfigure out which genes are responsible for the causeand means of infection, then they can target thosegenes with drug therapy.

A Vaccine for CancerMost people think of a virus as something that shouldbe avoided, but for years we have used weakened formsof viruses to combat smallpox, polio, chicken pox,measles, and mumps. Now researchers are hoping toadd cancer to that list.

Emptied of its contents, a virus’s capsid becomes adurable container capable of withstanding all sorts oftoxic environments and able to transport many dif-ferent chemicals and drugs to a specific location. Viralcontainers are already being used to deliver magneticmaterial to tumor cells so that they can be seen in mag-netic resonance imaging (MRI) tests, and they are nowbeing tested for use in delivering cancer cures.


The part of a virus that makes it a perfect medicaltool is its ability to target a specific type of cell. Thedrugs currently used to treat cancer circulate through-out the entire body. They act on healthy cells as wellas cancerous cells, causing many side effects that canbe quite severe. But viruses are very specific. They tar-get only the cells they are programmed to infect andleave other cells alone. Scientists around the world arelooking at ways to use the virus’s natural targeting char-acteristic to zero in on specific cancerous tumor cells.

At the Institute for Cancer Studies at BirminghamUniversity in England, researchers are working on anexperimental therapy using a genetically modifiedvirus as a homing device for cancer-killing drugs. It iscalled VDEPT, short for virus-directed enzyme prodrugtherapy.

The Future Under a Microscope 85

Researchers arestudying the use ofgenetically alteredviruses to target andeliminate cancerouscells like these lungcancer cells.

A patient would first be injected with the speciallydesigned virus that infects only cancer cells. Then aninjection of the prodrug is given. The prodrug is achemical that is harmless to healthy cells, but when itcomes in contact with the virus-infected cancer cell, itbecomes deadly. The cancer cells take it in, and thedrug is transformed into a toxic substance that kills thetumor cell instantly. Healthy cells remain unaffected.

Virus VectorsScientists are experimenting with viruses not only todistribute a needed vaccine but also to deliver healthy


genes to cells with a genetic disorder, a procedurecalled gene therapy. Gene therapy could help patientswho have a genetic disorder like cystic fibrosis or sickle-cell anemia, where only one or two missing or defec-tive genes are involved.

In gene therapy RNA retroviruses are first renderedharmless. Then the healthy genes are inserted into thevirus’s genome. The altered virus is then injected intothe tissue where it actively seeks out the appropriatecells to infect. As the RNA is copied by the cell’s repro-ductive machinery, it is also incorporated into the cell’sDNA.

This procedure is still in an experimental stage, butone of the first patients to benefit was an eighteen-month-old boy in England. He had a rare genetic dis-order called severe combined immunodeficiency thatprevented him from developing an immune system.He lived his first eighteen months in a plastic, sterilebubble room. Doctors removed bone marrow from theboy and used a virus to carry a new working versionof the missing gene into immune cells in the marrow.The marrow was put back into the boy’s leg, where itgradually started to produce healthy white cells thatnow protect the boy from infection.

One problem doctors must overcome is the unpre-dictability of where the new gene is inserted in the pa-tient’s DNA strand. If the placement is not exact, thenthe gene will not express itself. Scientists also have tobattle with the patient’s immune system, which seeksout and destroys these virus vectors before they get achance to deliver their genetic package.

Even though gene therapy is still in the experi-mental stage, it has caused much controversy. Manypeople are concerned about the safety of the proce-dure as well as the long-term effects of inserting avirus, even a disabled one, into a person’s body.

NanotechnologyViruses are making their mark in industry too, wherethey are being used as spare parts and miniature tools


in the growing field of nanotechnology. Nanotechnologyis the term given to research and engineering doneat an atomic or molecular level. Nano means one-billionth, and a nanometer is one-billionth of a meter.

Small is big in science. When Nobel Prize–winningphysicist Richard Feynman declared in 1960, “There’splenty of room at the bottom,” 28 he meant that tech-nology can always get smaller. In 1946, when the firstcomputer was constructed, it filled two thousandsquare feet of space and weighed fifty tons. Today thesmallest microcomputer would fit on the head of amatchstick, and the smallest microchip, unveiled in2003 by a Malaysian company, is no bigger than theperiod at the end of this sentence. But the smallertechnology gets, the more necessary it becomes tostudy those organisms that perform complex tasks onthat level every day—microbes.

“Scientists didn’t invent nanoscience,” says AngelaBelcher, a pioneering materials chemist at MassachusettsInstitute of Technology. “Organisms have been doingif for a long time.”29

An electron micrographshows an ant holdinga tiny microchip.Viruses can potentiallybe used to create evensmaller, more efficientmicrochips.

Belcher started out studying how sea snails madetheir beautiful mother-of-pearl shells. The snail stacksindividual molecules of calcium carbonate into layersto form a beautifully luminescent and very strongshell. Belcher uses the same technique of building anew material molecule by molecule, but she getsviruses to do the hard work for her.

Viruses make a good workforce because they haveevolved over millions of years to work perfectly at thenanoscale level. It is also easy to alter a virus’s geneticmaterial and instruct it to perform a specific task. Theviruses that Belcher and most nanoscientists use arebacteriophages because they infect only bacteria. Theseviruses are genetically modified to grow certain pro-tein receptors on their surface so that they are able tobind like a magnet to specific particles. This processtakes about three weeks.

One such virus strain is able to bind to zinc sul-phide, a semiconductor, which means it can transmitan electrical current. Billions of these specially madeviruses bind to billions of zinc particles. In a solution,viruses normally organize themselves in almost mil-itary precision so that they move freely withoutbumping into one another or creating a logjam. Asthese viruses with their zinc particles self-organize,they form an extremely thin film that can be pickedup out of the solution with a pair of tweezers. Thisthin film acts like the liquid crystal display on com-puter monitors. Belcher believes that her viruses cancreate stronger, smaller, and potentially more com-plex materials than those produced by man-made ma-chines. The process is also clean; it does not pollutethe environment.

In another lab researchers are working to perfect vi-ral wire. The bacteriophage viruses are altered to bindto other particles, but only at the ends of their long,skinny bodies. They latch on to each other, end toend, like children’s snap-together beads, forming longchains of microscopic semiconducting wire.


Silver-Making BacteriaCreating any kind of material on a nanoscale is costlyand complex, but if bacteria can collect particles of aprecious metal like silver, it could be invaluable. In aSwedish laboratory, scientists are working with an un-usual strain of bacteria that does just that. They crankout tiny crystals of silver.

Silver is usually toxic to most microbes and is usedin several bacteria-killing substances, but Pseudomonasstutzeri seems to thrive on it. This bacterium, whichis the same microbe that is used to clean paintings,was found growing on rocks in a silver mine. The bac-terium gathers up the metal and bundles it in distinctcrystal shapes at the edge of its cell. These microscopicsilver particles can then be harvested to construct ex-tremely thin, light-sensitive metal film or coatings forsolar collectors, or tiny optical and electronic devices.

Bacterial BatteriesHow could a tiny electronic device made out of mi-croscopic particles of silver be powered? Some re-searchers are taking their cue from the science fictionMatrix movies, in which humans are used as living bat-teries, and learning how to harness a living electricalsource. Fortunately they are not using humans, as themovies portray; instead, they are creating microbialfuel cells and bacterial batteries.

Like any living organism, bacteria take in and ex-pel energy. A colony of E. coli bacteria takes in carbo-hydrates, such as sugar, and breaks them down withenzymes. The bacteria release energy in the form ofhydrogen, the same substance that fuels “green” cars.The electrical current comes in the form of a steadyflow of electrons released as the microbe eats.

One company in England has made a fuel cell that isthe size of a personal CD player. The bacteria inside feedon sugar cubes. Chemical reactions strip electrons fromthe hydrogen atoms to produce a voltage that can poweran electrical circuit. To make it more cost-effective, re-


searchers are developing a second model that would befueled by organic waste material, such as the leftoversfrom lunch. Currently, the microbial fuel cell is beingused to power a small robot around the lab.

The U.S. Department of Defense is interested in an-other microbial fuel cell that uses a bacteria found onthe bottom of the sea floor. Rhodoferax ferrireducens canconvert more than 80 percent of the sugar it eats to elec-tricity. The process is slow. One cup of sugar can lightup a 60-watt bulb for seventeen hours, but the processto do so takes a week to charge up. The advantage tothis slow process is that once it gets going, the batterycontinues to work without interruption—a good qual-ity to have in a battery that is difficult to access. TheDepartment of Defense is eyeballing microbial fuel cellsto power electronic monitoring devices located at the


The electrical currentreleased as a microbeeats can be harnessedto create efficient fuelcells like this one.

bottom of the ocean. These fuel cells would run off ofthe organic sediment found on the sea floor.

Other fuel cells are being adapted to power medicalventilators and generate electricity for pacemakers.The pacemaker battery would run off of glucose, thesugar found in the pacemaker-wearer’s blood.

Microbial MotorsImagine a microscopic device propelled by a nanoscalemotor that could buzz through the body in search ofspecific cells. That is the target goal for engineers atCornell University. Researchers combined a moleculemade by a bacterium with one made by a scientist inthe lab. The result was a motor that operates similarlyto an E. coli bacterium turning its flagella on and off.

The E. coli uses the enzyme ATP to send signals toits flagella so that it can move around. Instead of fla-gella, researchers attached an engineered nanoscale ro-tor to act as the motor’s moving part. The rotor rotatesin response to electrochemical reactions with chargedparts of the ATP molecule. This specially designed E.coli bacterium could be tethered to a fixed spot andused as a tiny pump in industrial and medical devices.

The FuturePowering pacemakers with a bacterial battery, curingcancer with a virus, or cooking over a gas stove fueledby methane-producing microbes from the backyardseptic tank may seem far-fetched, but they could be-come common events in the future.

Each year we become more aware of the influence ofthe mighty microbe. Looking into the past, we see thatmicrobes have had the power to change human his-tory. Experiencing the infectious diseases of today, weknow that microbes can end a person’s life, diminish avillage’s population, and devastate a country’s econ-omy. But they can also be the solution to many of ourproblems in the future.

Whatever our technology needs may be or whateverproblems confront us—from emerging disease to en-


vironmental damage—there will be a microbe some-where that is able to help, but only if people are wiseenough to discover it. Such discoveries will take time.Scientists have only been aware of bacteria and theireffect on humans for less than three hundred years.And they have only scratched the surface of the worldof viruses. Their understanding of these microorgan-isms and their power continues to grow, along with anappreciation of what man and microbe can do together.Researchers can learn how to maintain the atmosphere


Although microbeslike this virus havecaused illness anddeath throughouthistory, the ability toharness their powerfor human benefitholds considerablepromise for the future.

from studying bacteria that have been doing just thatfor millions of years, and medical doctors can discoverhow to keep people healthy by examining the virusesthat infect them.

The key to harnessing bacteria and viruses for goodis to appreciate the possible consequences of the bad,because our relationship with the microbial world is atwo-way street. Humans’ behavior affects microbial be-havior, and vice versa. We might not see the next dev-astating infectious bacteria or virus barreling down onus, but with the use of other microbes, we will have thetools and knowledge to combat it. It is simple. Bacteriaand viruses are our worst enemies, yet they are also vi-tal for our survival. We live in a sea of invisible microbes,and we can either sink or swim.


Chapter 1: We Are Surrounded1. Quoted in Robert S. Boyd, “Despite Bad Reputation, Bacteria

Are Vital to Life,” Buffalo News, June 22, 2003, p. H-6.2. Quoted in Boyd, “Despite Bad Reputation,” p. H-6.3. J. William Schopf, Cradle of Life: The Discovery of Earth’s Earliest

Fossils. Princeton, NJ: Princeton University Press, 1999, p. 3.4. Quoted in Arno Karlen, Man and Microbes: Disease and Plagues

in History and Modern Times. New York: Putnam’s, 1995, p. 55.5. Quoted in Kathy A. Svitil, “Did Viruses Make Us Human?”

Discover, November 2002. www.discover.com.

Chapter 2: Early Discoveries6. Quoted in William M. Bowsky, The Black Death: A Turning Point

in History? New York: Holt, Rinehart & Winston, 1971, p. 13.7. Quoted in Bowsky, The Black Death, p. 13.8. Quoted in James Cross Giblin, When Plague Strikes: The Black

Death, Smallpox, AIDS. New York: HarperCollins, 1995, p. 70.9. Quoted in Giblin, When Plague Strikes, p. 76.

10. Quoted in Giblin, When Plague Strikes, p. 32.11. Quoted in History Learning Site, “Medicine in Ancient Rome,”

2002. www.historylearningsite.co.uk.12. Quoted in Warnar Moll, “Antonie van Leeuwenhoek Delft

Biography,” 2003. www.eronet.nl/users/warnar/leeuwenhoek.html.

13. Quoted in Moll, “Antonie van Leeuwenhoek.”14. Quoted in David M. Locke, Viruses: The Smallest Enemy. New

York: Crown, 1974, p. 20.

Chapter 3: Fighting an Invisible Enemy15. Quoted in Giblin, When Plague Strikes, p. 95.16. Quoted in Jenner Museum, “The Final Conquest of the

Speckled Monster,” 2003. www.jennermuseum.com.

Notes

95

17. Quoted in Pete Moore, Killer Germs: Rogue Diseases of theTwenty-first Century. London: Carlton, 2001, p. 7.

18. Quoted in Giblin, When Plague Strikes, p. 143.19. Quoted in Michael Shnayerson and Mark J. Plotkin, The Killers

Within: The Deadly Rise of Drug-Resistant Bacteria. Boston: Little,Brown, 2002, p. 35.

Chapter 4: Emerging Microbes20. Quoted in Boyd, “Despite Bad Reputation,” p. H-6.21. Quoted in Boyd, “Despite Bad Reputation,” p. H-6.22. Quoted in Nancy Shute, “SARS Hits Home,” U.S. News & World

Report, May 5, 2003, p. 40.23. Quoted in Stephen S. Hall, “On the Trail of the West Nile Virus,”

Smithsonian, July 2003, p. 94.

Chapter 5: Harnessing Invisible Power24. Quoted in Purdue News, “Munching Microbes Make a Meal

out of Toxic Substances,” April 1997. www.purdue.edu.25. The Guinness Book of World Records. Stamford, CT: Guinness

Media, 1998, p. 316.

Chapter 6: The Future Under a Microscope26. Daniel W. Drell, Anna Palmisano, and Marvin E. Frazier, “Micro-

bial Genomes: An Information Base for 21st Century Micro-biology,” U.S. Department of Energy, 2000. www.sc.doe.gov.

27. U.S. Department of Energy, Office of Science, Office of Biologicaland Environmental Research, “Microbial Genomics Research,”2003, p. 1.

28. Richard P. Feynman, “There’s Plenty of Room at the Bottom,”Engineering & Science, February 1960, p. 1.

29. Quoted in Deborah Smith, “Starting Small: Scientist UsesViruses as Building Blocks for New Technology,” SMH.com.au,2003. www.smh.com.au.


anaerobic: Without oxygen.

antibiotic: A substance that kills a bacterial infection.

bacteria: Microscopic one-celled organisms (bacterium: a single or-ganism).

bacteriophage: A virus that infects bacteria.

bioremediation: The process of cleaning up the environment usingmicrobes.

capsid: The protein coat of a virus.

cyanobacteria: A type of bacteria once called blue-green algae.

DNA (deoxyribonucleic acid): The genetic material, found in thenucleus of a living cell, that carries the information about an or-ganism and contains the codes needed to build proteins.

enzyme: A protein that controls chemical reactions.

flagella: Long, whiplike tails on some types of bacteria that allowthem to move.

genetic engineering: The alteration of genetic material in an or-ganism; involves the transfer of DNA from one cell to another.

genome: The complete sequence of DNA base pairs that code for aspecific organism.

lymphocyte: A type of white blood cell that produces antibodies.

microbe: A microscopic organism.

microbiology: The scientific study of microscopic organisms.

nanometer: An extremely small unit of measure; one-billionth of ameter.

Glossary

97

nanotechnology: Research and engineering performed at a molec-ular level.

pathogen: A disease-causing organism.

phagocyte: A type of white blood cell that engulfs and destroys harm-ful bacteria.

plasmid: A small, circular molecule of DNA found in bacteria.

spore: A single bacterial cell covered with a special protective coatthat allows it to remain in a resting state.

vaccine: A substance made from dead or weakened bacteria or virusesused to inoculate a person in order to prevent a disease and producean immunity to it.

vector: An animal or insect that carries a bacteria or virus but is notharmed by it.

virus: A disease-producing particle composed of genetic material cov-ered with a protein coat; a virus only can reproduce in a living cell.


BooksHoward and Margery Facklam, Bacteria. New York: Twenty-first

Century, 1994. A fascinating and easy-to-read description ofbacteria, their place in the world, and their effect on our lives.

———, Viruses. New York: Twenty-first Century, 1994. A conciseintroduction to the world of viruses and the scientists who dis-covered them.

Mark Friedlander, Outbreak: Disease Detectives at Work. Minneapolis:Lerner, 2000. Recounts the work performed by epidemiologistsfrom the Centers for Disease Control during infectious diseaseoutbreaks.

James Cross Giblin, When Plague Strikes: The Black Death, Smallpox,AIDS. New York: HarperCollins, 1995. Fascinating accounts ofthree major diseases and how they changed the world.

Cynthia S. Gross, The New Biotechnology: Putting Microbes to Work.Minneapolis: Lerner, 1988. A good introduction to genetic en-gineering and the use of bacteria in industry.

Lisa Yount, Epidemics. San Diego: Lucent, 2000. Discusses the re-turn of epidemics in modern times, the possible causes, and howthey are tracked and controlled.

Web SitesCenters for Disease Control and Prevention (www.cdc.gov).

Contains up-to-date information on emerging diseases and theCDC’s responses to them.

Digital Learning Center for Microbial Ecology (http://commtechlab.msu.edu). Very kid friendly; includes the Microbial Zoo,Microbe of the Month, and Microbes in the News.

For Further Reading

99

The Jenner Museum (www.jennermuseum.com). Provides an in-troduction to Edward Jenner, his life, and his work eradicatingsmallpox.

Microbe World (www.microbe.org). Run by the American Societyfor Microbiology; includes fun experiments as well as informa-tion about careers in microbiology.

Microbial Genomics Gateway (www.microbialgenome.org). Givesbackground information about microbes, their importance inthe world, and the Microbial Genome Project.

World Health Organization (www.who.int/en). Provides currentinformation on a variety of health issues that threaten peoplearound the world.


BooksNicholas Bakalar, Where the Germs Are: A Scientific Safari. New York:

Wiley, 2003. A vivid description of microbes encountered in every-day life.

Wayne Biddle, A Field Guide to Germs. New York: Holt, 1995. Shortexcerpts that describe the natural history of the microbes thatcause disease.

William M. Bowsky, The Black Death: A Turning Point in History? NewYork: Holt, Rinehart & Winston, 1971. Discusses the effect thatthe bubonic plague had on human civilization.

Bill Bryson, A Short History of Nearly Everything. New York: Broadway,2003. An entertaining compilation that includes one chapteron the power of microbes.

Paul De Kruif, Microbe Hunters. New York: Harcourt, Brace, 1953. Acollection of short biographies of famous and not-so-famous mi-crobiologists.

Bernard Dixon, Magnificent Microbes: An Astonishing Look Inside theMicroscopic World of Man’s Invisible Allies. New York: Atheneum,1976. A classic edition in microbiology that is written in lay-man’s terms by a trained microbiologist.

———, Power Unseen: How Microbes Rule the World. Oxford: Freeman,1994. A portrait gallery of seventy-five microbes and their char-acteristic behaviors.

David B. Dusenbery, Life at Small Scale: The Behavior of Microbes. NewYork: Scientific American Library, 1996. A comprehensive andtechnical book on bacteria and viruses.

The Guinness Book of World Records. Stamford, CT: Guiness Media,1998. This book contains records such as “World’s Largest Virus”that are interesting and sometimes obscure.

Works Consulted

101

Brent Hoff and Carter Smith, Mapping Epidemics: A Historical Atlasof Disease. New York: Franklin Watts, 2000. A fact-filled atlas ofdiseases throughout history.

Arno Karlen, Man and Microbes: Disease and Plagues in History andModern Times. New York: Putnam’s, 1995. Recounts man’s andmicrobes’ history from the first recorded encounter to the pre-sent day.

David M. Locke, Viruses: The Smallest Enemy. New York: Crown, 1974.This is an older book, but it effectively highlights the early dis-coveries in viral research.

Pete Moore, Killer Germs: Rogue Diseases of the Twenty-first Century.London: Carlton, 2001. An eye-opening account of antibiotic-resistant bacteria, emergent diseases, and bioterrorism.

Cynthia Needham, Mahlon Hoagland, Kenneth McPherson, and BertDodson, Intimate Strangers: Unseen Life on Earth. Washington, DC:ASM, 2000. A printed version of a National Science Foundationtelevision documentary of microbes’ role on Earth.

J. William Schopf, Cradle of Life: The Discovery of Earth’s Earliest Fossils.Princeton, NJ: Princeton University Press, 1999. An account ofthe discovery of the earliest fossils of bacteria found in Australia.

Michael Shnayerson and Mark J. Plotkin, The Killers Within: TheDeadly Rise of Drug-Resistant Bacteria. Boston: Little, Brown, 2002.A narrative account of doctors and research scientists who en-counter and battle drug-resistant bacteria.

Jack Uldrich and Deb Newberry, The Next Big Thing Is Really Small.New York: Crown Business, 2002. An introduction to nanotech-nology and its impact on industry.

PeriodicalsMichael Barletta, “Keeping Track of Anthrax,” Bulletin of the Atomic

Scientists, May/June 2002.

Robert S. Boyd, “Despite Bad Reputation, Bacteria Are Vital to Life,”Buffalo News, June 22, 2003.

David Brown, “Stopping a Scourge,” Smithsonian, September 2003.


Richard P. Feynman, “There’s Plenty of Room at the Bottom,”Engineering & Science, February 1960.

Jessica Gorman, “Microbial Materials,” Science News, July 5, 2003.

Stephen S. Hall, “On the Trail of the West Nile Virus,” Smithsonian,July 2003.

Claudia Kalb, “The Mystery of SARS,” Newsweek, May 5, 2003.

Michael Lemonick and Alice Park, “The Truth About SARS,” Time,May 5, 2003.

Anita Manning, “USA’s Disease Detectives Track Epidemics World-wide,” USA Today, July 25, 2001.

Marilynn Marchione, “Exotic Diseases Hit Home,” Buffalo News,June 22, 2003.

Nancy Shute, “SARS Hits Home,” U.S. News & World Report, May5, 2003.

Rebecca Skloot, “Angela Belcher,” Popular Science, November 2002.

John Travis, “Gut Check: The Bacteria in Your Intestines Are WelcomeGuests,” Science News, May 31, 2003.

U.S. Department of Energy, Office of Science, Office of Biological andEnvironmental Research, “Microbial Genomics Research,” 2003.

Internet SourcesTerry Devitt, “Study of Microbes May Hone Predictions of Mining

Impact,” News @ UW-Madison, 2000. www.news.wisc.edu.

Daniel W. Drell, Anna Palmisano, and Marvin E. Frazier, “MicrobialGenomes: An Information Base for 21st Century Microbiology,”U.S. Department of Energy, 2000. www.sc.doe.gov.

History Learning Site, “Medicine in Ancient Rome,” 2002. www.historylearningsite.co.uk.

Mark Horstman, “Bizarre Giant Virus Rewrites the Record Books,”News in Science, March 31, 2003. www.abc.net.au.

Works Consulted 103

Jennifer F. Hughes and John M. Coffin, “The Origin and the Sickeningof Our Species,” Popular Science, December 2001. www.popsci.com.

Jenner Museum, “The Final Conquest of the Speckled Monster,”2003. www.jennermuseum.com.

Rossella Lorenzi, “Bacteria Restores Ancient Italian Frescoes,” DiscoveryNews.com, June 20, 2003. http://dsc.discovery.com.

Warnar Moll, “Antonie van Leeuwenhoek Delft Biography,” 2003.www.eronet.nl.

Purdue News, “Munching Microbes Make a Meal out of Toxic Sub-stances,” April 1997. www.purdue.edu.

Rosalind Schrempf, “World’s Toughest Bacterium Has a Taste forWaste,” http://pnl.gov.

Seattle Times, “Therapy Uses Viruses as Natural Antibiotics,” June 17,2003. http://seattletimes.nwsource.com.

Deborah Smith, “Starting Small: Scientist Uses Viruses as Building Blocksfor New Technology,” SMH.com.au, 2003. www.smh.com.au.

Kathy A. Svitil, “Did Viruses Make Us Human?” Discover, November2002. www.discover.com.

U.S. Geological Survey, “Bioremediation: Nature’s Way to a CleanerEnvironment,” 2002. http://water.usgs.gov.


Adenovirus, 17Aedes aegypti, 36–37Agrobacterium tumifaciens, 71AIDS (acquired immuno deficiency syndrome), 10, 19,63, 64

air travel, 59American Society forMicrobiology, 10

anaerobic bacteria, 67, 74, 83aniline dye, 33, 45anthraxancient viruses and, 13, 54bioterrorism and, 65–66dormant spores of, 15isolation of, 32–34

antibioticsdigestive problems and, 23–24disease control and, 51function of, 45–47resistance to, 52–53see also specific names of antibiotics

antibodies, 40, 45arboviruses, 60–61Arctic, 10–11, 16, 83Aretino, Spinello, 79arsenic compound 606, 45artwork, cleaning of, 79–80, 90Aspergillus niger, 70ATP (adenosine tri-phosphate),92

Australian National University,11

bacilli, 13Bacillus subtilis, 70bacteriaanatomy of, 13, 15–16beneficial types of, 10, 39breeding environment of,10–11

dormant forms of, 15–16movement of, 14–15nitrogen-fixing, 21oil-eating, 74–76reproduction of, 18–19silver-making, 90species of, 13–15temperatures and, 74, 82–83

bacterial plasmid, 68Bacteriological and ToxicWeapons Convention, 65

bacteriophages, 17, 37, 52–53,89

Beijerinck, Martinus, 34–36Belcher, Angela, 88–89benzene, 76binary fission, 18–20biocontainment unit, 59biomining, 72–74bioprocessing, 69bioreactors, 69bioremediationfuel spills and, 76–77industrial plants and, 76military ammunition sites and,76

mining sites and, 78oil spills and, 74–76

Index

105

radioactive sites and, 79toxic waste cleanup and, 82

bioterrorism, 64–66Black Death. See bubonic plagueblue-green algae. Seecyanobacteria

Boccaccio, Giovanni, 29boils, 15Borrelia burgdorferi, 60botulin, 66Bristol-Meyers Pharmaceuticals,47–48

bubonic plague, 25–29Burkholder, Paul, 48Bush, George W., 66

cancer, 84–86carbon dioxide, 82–83cellsantibiotics and, 45–46bacteria composition and, 13genetic engineering and, 68,71

genomes and, 81–82HIV and, 63injured, 39memory, 40, 45microbial fuel, 90–92

cellulose, 22–23Centers for Disease Control andPrevention (CDC), 9, 50, 57,63–64

Chain, Ernst Boris, 46Charleston, South Carolina, 76chemical spills. Seebioremediation

chicken cholera, 34chicken pox, 40, 44, 84China, 8–9Chloromycetin, 48cholera, 53, 56–57citric acid, 70

cocci, 13colds, 17Conversion and Battle of SaintEfisio (Aretino), 79

copper industry, 72–73coronavirus, 17cowpox, 42Cradle of Life (Schopf), 12creosote, 78crown gall disease, 71crystallization, 38cyanide, 78cyanobacteria, 14, 76cystic fibrosis, 87

DDT, 78decomposition, 21–22, 32deer tick, 60Deincoccus radiodurans, 79dengue fever, 60d’Herelle, Felix, 52–53diabetes, 70digestion, 22–23, 39, 70dinosaur extinction, 13diphtheria, 46diplo, 13diseasesantibodies and, 40drug therapy and, 84spread of, 54–56

study of, 57–59weather and, 62

vaccines and, 43–45Division for Emerging andOther Communicable Diseases,57

DNA (deoxyribonucleic acid)antibiotics and, 46cell reproduction and, 19genome and, 24viral, 16–19, 24, 37, 72see also genetic engineering


Drell, Daniel W., 82

Ebola virus, 17E. coli, 14, 90, 92ecosystem, 20–21, 24Ehrlich, Paul, 45electrical conductors. Seenanotechnology

Eliava Institute, 53encephalitis, 60environmental contamination.See groundwater contamination

epidemics, 25–28epidemiologists, 57–59Escherichia coli. See E. colievolution, 13Exxon Valdez (oil tanker), 74–75

fermentation, 31–32, 67Feynman, Richard, 88Finlay, Carlos Juan, 36flagella, 14–15, 92Fleming, Alexander, 46–48,51–52

Florey, Howard Walter, 46flu, 10, 17, 44foodchain, 11fermentation and, 67genetic engineering and,68–72

foot-and-mouth disease, 36fossils, 13Frosch, Paul, 36

gene therapy, 86–87genetic engineeringagriculture and, 71–72drugs and, 70–71long-term effects of, 72mining and, 74process of, 68

Genome for Life, 82genome projects, 81–84germ banks, 66germ theory, 33–34Gibbs, Adrian, 11Global Public HealthIntelligence Network, 57

global warming, 82–83gold processing, 73–74Great Pestilence. See bubonicplague

groundwater contaminationgasoline and, 77mining microbes and, 78oil-eating bacteria and, 74–76wastewater treatment and, 74see also bioremediation

Guinness Book of World Records,The, 79

Heatley, Norman G., 46Heymann, David, 59high-fructose corn syrup, 70histamine, 39HIV (human immunodeficiencyvirus), 17, 19, 63–64

Homestake Mine, 78hoof-and-mouth disease, 70horizontal gene transfer, 51Hudson River, 74human growth hormone, 70Hunt, Mary, 46–47

immune systemchemical releases and, 39–40HIV and, 63–64human body’s defenses and,39

immune response and, 41, 43vaccines and, 42–45

influenza. See fluingrafting, 41–42

Index 107

inoculations. See ingraftingInstitute for Cancer Studies, 85insulin, 70intestinal tract infections, 17Ivanovski, Dmitri, 34–36

Jenner, Edward, 42–43, 49Jerome L. and Dawn GreeneInfectious Disease Laboratory,61

Kautzer, Schyan, 54Knott, Max, 38Koch, Robert, 31–32, 45Koch’s postulates, 33–34

lactic acid, 67, 70Lactobacillus bulgaricus, 70Leeuwenhoek, Antoni van,30–31

Leuconostoc, 67Lipkin, Ian, 61lock-and-key system, 19Loeffler, Friedrich, 36Lyme disease, 60lymphocytes, 40

malaria, 60Matrix (films), 90Mayer, Adolf, 34McDonald, John, 24measles, 44, 84Meister, Joseph, 43meningitis, 46Merck & Company, 49methane, 84Methanococcus jannaschii,83–84

Microbial Genome Project,81–82

microbiology, 30microscopes

bacterial observance and,30–31

electron, 16, 38Mina Al-Ahmadi terminal,75–76

mining industry, 72–74, 78, 90mitochondria, 19mold, 46–49, 67monkeypox, 54–56Montagu, Lady Mary Wortley,41–42

mosaic viruses, 34–38, 71mosquitoes, 36, 61MRI (magnetic resonance imaging), 84

mummies, 12–13mumps, 44, 84mutation, 51, 55, 72

nanotechnologyE. coli bacterium and, 92microbial fuel cells and,90–92

microchips and, 88silver-making bacteria and, 90

Nelmes, Sarah, 42Newsweek (magazine), 51New York City HealthDepartment, 60

New York Times (newspaper), 52Nies, Loring, 77nitrogen, 21North River wastewater treat-ment plant, 74

nose spots, 14–15

Oak Ridge Laboratory, 78–79Old Lyme, Connecticut, 60Olds, G. Richard, 56

Pacific Ocean, 11Pasteur, Louis, 31–34, 43, 67


PCBs (polychlorinatedbiphenyls), 78

penicillin, 46–48, 52Penicillium chrysogenum, 47Persian Gulf War, 75–76Petri, Julius, 33petri dish, 33, 35Phage therapy, 52–53phagocytes, 40Phipps, James, 42photosynthesis, 14plague, 10, 13, 25–29plants, 20–21plasmids, 51pneumoniaantibodies and, 40host cells and, 19penicillin and, 46, 52

polio, 13, 44, 54, 84protease, 70protein, 82, 84Pseudomonas stutzeri, 79, 90

rabies, 34, 43radiation, 12, 79Rajneesh cult, 66Reed, Walter, 36–37Renaissance, 27respiratory infections, 17Rhizobium, 21Rhodoferax ferrireducens, 91riboflavin, 70RNA (ribonucleic acid)gene therapy and, 87genetic engineering and, 68HIV and, 63microbial multiplication and,19

virus composition and, 16–17Rocky Mountain spotted fever,48

Royal Society of London, 31

rubella, 44Ruska, Ernst, 38

Sabin, Albert, 44Salk, Jonas, 44salmonella, 40salmonella typhosa, 15Salyers, Abigail, 10SARS (severe acute respiratorysyndrome), 8–9, 17, 57–59

scarlet fever, 46Schopf, J. William, 12septicemia, 52severe combined immunodeficiency, 87

sickle-cell anemia, 87Siena (Italy), 25silkworm disease, 32–33Sitala, 29–30skin, 39–40smallpoxepidemic of, 27–28eradication of, 49ingrafting and, 40–42stored samples of, 49–50vaccines and, 84

Snow, John, 56–57soil, 11, 48sore throats, 15spirilla, 13spirochaeta, 15spirochete, 45, 60spores, 15–16Stanley, Wendell, 38staphylo, 14staphylococcus, 15, 46Steward, William H., 51strepto, 14streptococcus, 15streptomycin, 49Synechococcus, 83syphilis, 15, 45

Index 109

TCE (trichloroethylene), 78tetanus, 44Theiler, Max, 43–44Thiobacillus ferooxidans, 73Tropical Disease and TravelMedicine Center, 56

tuberculosis, 34, 45, 49Tura, Agnolo di, 25–26typhoid fever, 15, 53typhus, 48

United Nations, 49United Statesbiological warfare and, 65Department of Agriculture(USDA), 46–48

Department of Defense (USDOD), 91

Department of Energy (DOE),79, 81–84

gasoline, contaminatedgroundwater and, 77

Geological Survey (USGS), 76,78

monkeypox and, 55phage therapy and, 53smallpox samples and, 49–50

vaccinations, 40, 42, 49–50, 66vaccines, 34, 42–44, 45, 84variola, 27Varro, Marcus Terentius, 30VDEPT (virus-directed enzymeprodrug therapy), 85–86

viral replication, 37viral wire, 89viruses, 16ancient, evidence of, 12–13arthropod-borne, 60attack methods of, 18–19beneficial functions of, 24environmental changes and,59–60

filterable, 36reproduction of, 19–20

virus vectors, 68vitamins, 69–70

Waksman, Selman, 49Wenzel, Richard, 51West Nile virus, 60–62, 63Whitewood Creek, 78Whitmarsh, Eileen, 54World Federation for CultureCollections, 66

World Health Organization(WHO), 9, 49–50, 57–59, 64

World Trade Center attack(2001), 66

World War II, 79World Wide Web, 57

X-ray crystallography, 38

yeast, 67yellow fever, 36–37, 43–44, 60Yersinia pestis, 25

zinc sulphide, 89


Cover photo: Andrew Syred/Photo Researchers, Inc.Anthony Annandono, 62© Bettmann/CORBIS, 50Colin Braley/Reuters/Landov, 65CAMR/A.B. Dowsett/Photo Researchers, Inc., 32© Clouds Hill Imaging Ltd./CORBIS, 61CNRI/Photo Researchers, Inc., 53© CORBIS, 93© Corel Corporation, 11Digital Stock, 72© Natalie Fobes/CORBIS, 75© Hulton/Archive by Getty Images, 29Richard I’anson/Lonely Planet Images, 55Chris Jouan, 15, 17, 18, 37, 47, 86© Michael S. Lewis/CORBIS, 73Maximilian Stock Ltd./Photo Researchers, 69NIBSC/Photo Researchers, Inc., 64© Gianni Dagli Orti/CORBIS, 26Photo Researchers, Inc., 31, 35Philippe Psaila/Photo Researchers, Inc., 58© David Sailors/CORBIS, 77Francoise Sauze/Photo Researchers, Inc., 48© Scala/Art Resource, 12Martha Schierholz, 41, 44Volkar Steger/Photo Researchers, Inc., 91Andrew Syred/Photo Researchers, Inc., 88© Sandro Vannini/CORBIS, 80VVG/Photo Researchers, Inc., 23, 85© Randy Wells/CORBIS, 83Thomas White/Reuters/Landov, 8

Picture Credits

111

Peggy Thomas is the author of ten nonfiction books for childrenand young adults as well as numerous magazine and newspaper ar-ticles. Several of her books have been placed on the New York PublicLibrary’s recommended list of Books for the Teen Age and listed asan NSTA-CBC Outstanding Science Trade Book for Children. Thomasreceived her master’s degree in anthropology from the StateUniversity of New York at Buffalo and lives in Middleport, New York,with her husband and two children.

About the Author

112

Documents

by Peggy Thomasndl.ethernet.edu.et/bitstream/123456789/1652/1/111.pdf.pdf · 2018. 9. 17. · Thomas, Peggy. Bacteria and Viruses / by Peggy Thomas. v. cm. Ñ (Lucent library of science