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The Microbial World and You



What is Microbiology?

Microbes, or microorganisms are minute

living things that are usually unable to be

viewed with the naked eye.

What are some examples of microbes?

Bacteria, fungi, protozoa, algae, viruses

are examples!

Some are pathogenic

³Germ´ refers to a rapidly growing cell.




Microbes:

Decompose organic waste

Are producers in the ecosystem byphotosynthesis

Produce industrial chemicals such asethyl alcohol and acetone

Produce fermented foods such as vinegar,cheese, and bread



: Introduction to Microbiology, History & scope

Microbiology:

- In the broadest sense, microbiology is the study of all organisms that are invisible to

the naked eye-that is the study of microorganisms.

- Its subjects are viruses, bacteria, many algae and fungi, and protozoa.

- The importance of microbiology and microorganisms can not be overemphasized.

- Microorganisms are necessary for the production of bread, cheese, beer, antibiotics,

vaccines, vitamins, enzymes, etc.

- Modern biotechnology rests upon a microbiological foundation.

Microorganisms:

- Microorganisms are everywhere; almost every natural surface is colonized by

microbes, from body to ocean. Some microorganisms can live hot springs, and others in

frozen sea ice.

- Most microorganisms are harmless to humans; You swallow millions of microbes

every day with no ill effects. In fact, we are dependent on microbes to help us digest our food.

- Microbes also keep the biosphere running by carrying out essential functions such as

decomposition of dead animals and plants. They make possible the cycles of carbon,

oxygen, nitrogen and sulfur that take place in terrestrial and aquatic systems.

- Microorganisms have also harmed humans and disrupted society over the millennia.







Knowledge of Microbes allows humans to

Prevent food spoilage

Prevent disease occurrence

Led to aseptic techniques to prevent

contamination in medicine and in

microbiology laboratories.



History of Microbiology

Ancestors of bacteria were the first life on Earth.




The first microbes were observed in 1673.

In 1665, Robert Hooke (Englishman) reportedthat living things were composed of little

boxes or cells.




1673-1723, Antoni van

Leeuwenhoek (Dutch)

described live

microorganisms thathe observed in teeth

scrapings, rain water,

and peppercorn

infusions.




Many believed spontaneous generation:

life can arise from non-living matter

In 1668, the Italian physician Francesco

Redi performed an experiment to disprove

spontaneous generation.

Can you think of an experiment that could

disprove spontaneous generation?




Conditions Results

3 jars covered with fine

net

No maggots

3 open jars Maggots appeared

From where did the maggots come?

What was the purpose of the sealed jars?S pontaneous generation or biogenesis?

Redi filled six jars with decaying meat.



Supported by:

Aristotle (384-322 BC) ± Believed that simple invertebrates

could arise by spontaneous generation

John Needham (1713-1781) ± Boiled mutton broth, then

sealed and still observed growth after a period of time

LazarroS

pallanzani (1729-1799) No growth in sealed flask after boiling ± proposed that air was needed for growth of

organisms

Felix Pouchet (1859) ± Proved growth without

contamination from air



Disproved by:

Francesco Redi (1626-1697) ± maggotunable to grown on meat if meat was

covered with gauze Schwann, Friedrich Schroder and vonDusch (1830s) ± Air allowed to enter flask but only after passing through a heated

tube or sterile wool

John Tyndall (1820-1893) ± Omission of dust no growth. Demonstrated heatresistant forms of bacteria (endospores)



Spontaneous Generation Myths

Snakes from horse hairs in stagnant water

Mice from grain and cheese wrapped in a sweater

Maggots from rotting meat

Fleas from hair

Flies from fresh and rotting fruit Mosquitoes from stagnant pondwater

Eels from slimy mud at the bottom of the ocean

Locusts from green leaves

Raccoons from hollow tree trunks

Termites are generated from rotting wood




Rudolf Virchow (German) presented

biogenesis: living cells can arise only from

preexisting cells.




So now there are two hypotheses:

The hypothesis that living organisms arise

from nonliving matter is called spontaneousgeneration. According to spontaneous

generation, a ³vital force¶ Forms life.

The Alternative hypothesis, that the living

organisms arise from preexisting life, is

called biogenesis.




1861: Louis Pasteur demonstrated that

microorganisms are present in the air.

Conditions ResultsNutrient broth placed in

flask, heated, not sealed

Microbial growth

Nutrient broth placed in

flask, heated, thensealed

No microbial growth

S pontaneous generation or biogenesis?




Next experiment, Pasteur¶s S-shaped flask kept

microbes out but let air in. These experiments

form the basis of aseptic technique






The Golden Age of Microbiology

1857-1914

Beginning with Pasteur¶s work, discoveries

included the relationship between microbes

and disease, immunity, and antimicrobialdrugs




Pasteur showed that microbes are

responsible for fermentation.

Fermentation is the conversation of sugar toalcohol to make beer and wine.

Microbial growth is also responsible for

spoilage of food.

Bacteria that use alcohol and produce acetic

acid spoil wine by turning it to vinegar (acetic

acid).




Pasteur demonstrated that

these spoilage bacteria

could be killed by heat that

was not hot enough to

evaporate the alcohol in

wine. This application of a

high heat for a short time

is called pasteurization.




The Germ Theory of Disease

1835: Agostino Bassi showed a silkworm

disease was caused by a fungus.

1865: Pasteur believed that another silkworm

disease was caused by a protozoan.

1840s: Ignaz Semmelwise advocated

handwashing to prevent transmission of

puerperal fever from one patient to another.



Chapter 1 The Microbial World and You



1860s: Joseph Lister used a chemical

disinfectant to prevent surgical woundinfections after looking at Pasteur¶s work

showing microbes are in the air, can spoil

food, and cause animal diseases.





1876: Robert Koch provided proof that a

bacterium causes anthrax and provided the

experimental steps, Koch¶s postulates, used

to prove that a specific microbe causes a

specific disease.

Koch was a physician and Pasteur¶s youngrival



K och¶s Postulates:

- Microorganism must be present in every case of the disease but absent from healthy

individuals.

- The suspected microorganism must be isolated and grown in pure cultures.

- The disease must result when the isolated microorganism is inoculated into a healthy

host.

- The same microorganism must be isolated from the disease host.

Isolation of Microorganisms:

- During Koch¶s studies, it became necessary to isolate suspected bacterial pathogens.- He cultured bacteria on the sterile surfaces of cut, boiled potatoes Not satisfactory.

- Regular liquid medium solidified by adding gelatin gelatin melted @ T>28°C.

- Fannie Eilshemius suggested use of agar; 100°C to melt, 50 °C to solidify.

- Richard Petri developed petri dish, a container for solid culture media.



Louis Pasteur (1822 1895):

- Developed vaccines for Chickenpox, anthrax, rabies

- Demonstrated that all fermentations were due to theactivities of specific yeasts and bacteria.- Developed Pasteurization to preserve wine duringstorage. Important: Foods

- Discovered that fermentative microorganisms wereanaerobic and could live only in absence of oxygen.



OtherDevelopments«

- Winogradsky made many contributions to soil microbiology; discovered that soil

bacteria could oxidize Fe, S and ammonia to obtain energy.

- Isolated Anaerobic nitrogen-fixing bacteria; studied the decomposition of cellulose.

- Together with Beijerink , developed the enrichment-culture technique and the use of selective media.

- Early 40¶s, Microbiology established closer relationship with Genetics and

Biochemistry; microorganisms are extremely useful experimental subjects.

- e.g. Study of relationship between genes and enzymes; evidence that D NA is the

genetic material;- Recently, Microbiology been a major contributor to the rise of Molecular Biology.

- Studies on Genetic code; mechanisms of D NA, R NA, and Protein synthesis;

regulation of gene expression; control of enzyme activity.

- Development of RecombinantDNA Technology and Genetic Engineering.



Scope of Microbiology:

- Many microbiologists are primarily interested in the biology of microorganisms, while others focus on specific groups;

- Microbiology has an impact on medicine, agriculture, food science, ecology,

genetics, biochemistry, immunology, and many other fields.

- Virologists - viruses

- Bacteriologists - bacteria

- Phycologists ± algae

- Mycologist -fungi

- Protozoologists ± protozoa



- Medical Microbiology: deals with diseases of humans and animals; identify and plan

measures to eliminate agents causing infectious diseases.

- Immunology: study of the immune system that protects the body from pathogens.

- Agricultural Microbiology: impact of microorganisms on agriculture; combat plant

diseases that attack important food crops.

- Food and Dairy Microbiology: prevent microbial spoilage of food & transmission of

food-borne diseases (e.g. salmonellosis); use microorganisms to make food such as

cheeses, yogurts, pickles, beer, etc.

- Industrial Microbiology: using microorganisms to make products such as antibiotics,

vaccines, steroids, alcohols & other solvents, vitamins, amino acids, enzymes, etc.

- Genetic Engineering: Engineered microorganisms used to make hormones,

antibiotics, vaccines and other products.

- Since viruses are acellular and possess both living and nonliving characteristics, theyare considered neither prokaryotic nor eukaryotic. They will be discussed in separate

section of the course.

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