Introduction

What are microbes? Where can they be found? How big are they?

Fig. 1.7

Types of Microbes

They include– Bacteria– Protozoa– Fungi– Algae– *Helminths– *Viruses– *Prions

Bacteria

Unicellular Prokaryotic Cell walls contain peptidoglycan Have many shapes Generally reproduce by binary fission Obtain nourishment from organic or inorganic

substances of photosynthesis

Archaea

Prokaryotic cells Cell walls lack peptidoglycan (if present) Not known to cause human disease Mainly found in extreme environments

Fungi

Eukaryotes May be multicellular or unicellular May reproduce sexually or asexually Obtain nourishment by absorbing organic

material from their environments Cell walls composed of chitin

Protozoa

Eukaryotes Unicellular Classified by type of movement May live as free entities or parasites May reproduce sexually or asexually

Algae

Photosynthetic eukaryotes May produce sexually or asexually May be unicellular or multicellular Cell walls composed of cellulose

Helminths

Multicellular animal parasites

Viruses

Acellular organisms Composed mainly of protein and nucleic

acid; may contain lipids Obligate intracellular parasites

Prions

Proteinaceous infectious particles Composed of protein

6 processes that define life

1. growth2. reproduction & heredity3. metabolism4. movement and/or irritability5. capacity to transport substances into & out

of cell6. cell support, protection & storage

mechanisms

History of Microbiology

Supernatural Miasma theory- disease is caused by an

altered chemical in the air Zaccharias Jansen created the first

microscope (1600). No technology prior to this

Modification of Microbe Definition

Thiomargarita nambiensis- large enough to be seen without a microscope

Viruses and prions- not living organisms

Microbes are easier to study

Microorganisms are easier to study than macroorganisms (organisms visible with the naked eye) because of – Relative simplicity– Rapid reproduction– Adapatility

History of Microbiology

Antoni van Leeuwenhoek- discovered “animalcules”

Robert Hooke- (1678)- developed the compound microscope; confirmed Leeuwenhoek’s findings; marked the beginning of the cell theory

Spontaneous Generation

Spontaneous generation- theory that living things arise from nonliving things

Debate of this theory

Francesco Redi

In his experiment, he used 3 jars containing meat and left the jar open. He took 3 other jars containing meat and sealed them. Days later, only the open jar contained organisms. Opponents said sealing the jar prevented fresh air to enter, therefore, microbes could not grow. He modified his experiment using a mesh gauze, which was thin enough to allow air, but prevent microbes.

Fig. 1.p010

John Needham

Boiled nutrient broth and placed them into sealed containers. Days later, microbes grew.

What are some reasons this may have happened?

Lazarro Spallanzani

In his experiment, he sealed flasks of nutrient broth then boiled them. He transferred the broth into sealed containers and no microbes grew. Needham suggested the “vital force” needed for microbes to grow was kept out of the flask by the seals

Laurent Lavosier

Showed importance of oxygen to life. Spallanzani opponents claimed there wasn’t enough oxygen to support life in his sealed flasks

Shultz and Schwann

Thought air was the source of microbes. The passed air through chemicals into heat treated flasks. No microbes grew. Opponents said the chemicals prevented microbial growth

Louis Pasteur

Louis Pasteur resolved the debate of spontaneous generation. He set up flasks with beef broth, boiled them and left them open. Other flasks containing boiled beef broth were sealed. A few days later, microbes were present in the open flasks, but not the sealed ones. Pasteur suggested that microbes are present in the air and are capable of contaminating non living solutions. Then, he set up another series of flasks with boiled beef broth containing an S shaped opening. A few days later, no microbes were present.

Louis Pasteur

These S shaped flasks allowed air to enter (filling the oxygen requirement), but prevented microbes from entering (they are presumably “caught” in the S shaped openings). He showed microbes are present in air and can contaminate sterile solutions, but the air itself does not create microbes. He also showed these microbes can be destroyed by heat or microbial access can be blocked. These discoveries formed the basis of aseptic techniques- techniques used to prevent microbial contamination

Louis Pasteur

Showed microbes caused fermentation & spoilage

Disproved spontaneous generation of m.o.

Developed aseptic techniques.

Developed a rabies vaccine.

(1822-1895)

The Golden Age of Microbiology (1857-1914)

During this time rapid advances in microbiology were made and spearheaded by Pasteur and Robert Koch

Were possible due to advances in microscopy and other technology of the Industrial Revolution

Germ Theory of Disease

Many diseases are caused by the growth of microbes in the body and not by sins, bad character, or poverty, etc.

Aseptic Techniques

Ignaz Semmelweis showed that physicians who do not disinfect their hands can transmit disease to patients.

Joseph Lister began using phenol as a disinfectant. The number of deaths from childbirth fever decreased.

Robert Koch

Robert Koch (1876) set out to discover the causative agent of anthrax. He took a sample of blood from cattle that died of anthrax and cultured it. Samples from the culture were then injected into healthy animals. After these animals became sick and died, he isolated the bacteria in their blood and cultured it. He found that both sets of organisms were identical. This experiment established a sequence of steps for relating a specific organism to a specific disease. These steps are known as Koch’s postulates

Koch’s Postulates

1) the same pathogen must be present in every case of disease

2) pathogen must be isolated from diseased host and grown in pure culture

3) pathogen from pure culture must cause disease when inoculated into a healthy susceptible laboratory animal

4) pathogen must be isolated from inoculated animal and must be shown to be the original organism

Robert Koch

Established a sequence of experimental steps to show that a specific m.o. causes a particular disease.

Developed pure culture methods.

Identified cause of anthrax, TB, & cholera.

(1843-1910)

Edward Jenner

Edward Jenner (1796) discovered from milkmaids that those who contracted cowpox became mildly ill, but never contracted smallpox. Jenner decided to determine the validity. He obtained permission to use an 8 year old “volunteer” and inoculated him with scrapings from cowpox pustules. The child became ill, but never got smallpox. This process was termed vaccination. Protection from the disease or recovery from the disease is called immunity.

Louis Pasteur

Pasteur (1880) found that aged microbes also confer immunity. He was working on isolating the causative agent of cholera using chickens. He inoculated chickens with cholera and they became sick and died. Allegedly, he went away for the summer, and his cholera samples aged. When he came back, he used these aged cultures to inoculate the chickens. These chickens became mildly ill but did not die. Then (allegedly) he inoculated these same chickens with a regular strength batch since he ran out of new chickens. He found that these chickens did not get sick at all. He determined these aged cultures lost the ability to cause disease and was able to confer immunity.

Magic Bullet

Paul Ehrlich (1910) speculated about a “magic bullet”, a chemical which could destroy a pathogen without affecting the host. Prior to this, the only chemical being used was quinine, to treat malaria. Ehrlich eventually discovered salvarsan, effective against syphilis.

Alexander Fleming

(1928), while doing experiments, left a Petri dish which became contaminated by mold. He noted an area of inhibition around the mold, an area where no bacterial growth occurred. However, the usefulness of this mold, used to produce penicillin, did not occur until the 1940s.

Types of Study

Bacteriology- study of bacteria Mycology- study of fungi Parasitology- study of parasites Immunology- study of the immune system Virology- study of viruses Phycology (algology)- study of algae Protozoology- study of protozoa

Benefits of Microbes

Recycle vital elements Recycle water Bioremediation Pest control Food

Emerging Infectious Disease

EID’s may occur due to:– evolutionary changes to existing organisms– spread of diseases to new geographic regions – increased human exposure to new diseases in areas undergoing

ecological change (construction, deforestations) – increased number of patients with depressed immune systems – disruptions in human population, such as crowding or immigration – lack of immunization – lack of nourishment– mass production and packaging of food – animal migration

People Involved in Classification

Charles Darwin (1859) proposed the theory of natural selection

Carolus Linnaeus (1735-1759)- divided organisms into plant and animal and created a 2 name system

Carl von Nageli (1857)- proposed bacteria and fungi be placed into the plant kingdom

Ernst Haeckel (1866)- proposed kingdom Protista to include bacteria, protozoa, algae and fungi; Fungi were placed into their own kingdom in 1959

Robert G. E. Murray (1968)- proposed the kingdom Prokaryotae

Evolution- living things change gradually over millions of years

Changes favoring survival are retained & less beneficial changes are lost.

All new species originate from preexisting species.

Closely related organism have similar features because they evolved from common ancestral forms.

Evolution usually progresses toward greater complexity.

Naming micoorganisms

Binomial (scientific) nomenclature Gives each microbe 2 names

– Genus - noun, always capitalized– species - adjective, lowercase

Both italicized or underlined– Staphylococcus aureus (S. aureus)– Bacillus subtilis (B. subtilis)– Escherichia coli (E. coli)

More Classification

Robert Whittaker (1969)- proposed a 5 kingdom system– Monera (Prokaryotae)- bacteria– Protista-protozoa and algae– Fungi-yeasts, molds– Plantae-plants– Animalia-vertebrates, invertebrates

Carl R. Woese (1978) proposed 3 domains to be placed above kingdom

Fig. 1.15

Taxonomy - system for organizing, classifying & naming living things

Domain - Archaea, Bacteria & Eukarya Kingdom - 5 Phylum or Division Class Order Family Genus species

3 domains

Eubacteria -true bacteria, peptidoglycan Archaea –odd bacteria that live in extreme

environments, high salt, heat, etc Eukarya- have a nucleus, & organelles

Methods of Classifying and Identifying Microbes

Chapter 4 pgs 107-108 Bergey’s Manual of Determinative Bacteriology Morphological Characteristics Differential Staining Biochemical Tests Serology DNA base composition Using rRNA sequencing,

Scientific Method

Form a hypothesis - a tentative explanation that can be supported or refuted by observation & experimentation

A lengthy process of experimentation, analysis & testing either supports or refutes the hypothesis.

Results must be published & repeated by other investigators.

Scientific Method

If hypothesis is supported by a growing body of evidence & survives rigorous scrutiny, it moves to the next level of confidence - it becomes a theory

Evidence of a theory is so compelling that the next level of confidence is reached - it becomes a Law or principle

Fig. 1.11