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1Lecture Objectives:

Why study microbiology?

What is microbiology?

Roots of microbiology

Why study microbiology?

MEDICALENVIRONMENTAL

APPLIED SCIENCE BASIC SCIENCE

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The science of microbiology

Microbiology

Genetics

PhysiologyMolecular Bio

Biochem.

Ecology

ChemistryComputer Sci.

Engineering

Microbiology can be highly interdisciplinary

Geology

What is Microbiology

• Study of life too small to be seen

unaided by eye

! Need a microscope to see

them

•Using techniques of microbiology

!Isolate microorganisms

!Study their characteristics

<0.1 mm too small to see

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Where to find microbes?

Ex. 1. In nature:

Where to find microbe?

Ex. 2. In your intestines:

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Characteristics of a living organism

All living organisms are composed of one or

more cells—the cell theory of life.

Viruses are not cellular, and are not

considered to be living organisms. They are

still considered a microorganism.

Characteristics of life

Cell: The fundamental unit of living organisms with

characteristic functions and structures.

Cell functions:

1. Metabolism—biochemical reactions catalyzed byenzymes

2. Reproduction

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Characteristics of life

3. Differentiate

! Formation of a spore; part of cell life cycle.

4. Communicate

! Or interact by means of chemicals released or taken

up

Characteristics of life

5. Movement

! Living organisms are often capable of self-propulsion

6. Evolve

! Cells evolve to display different or new biological

properties.

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Characteristics of life

Cells have structures:

• Cytoplasm—aqueous fluid containing

enzymes, organelles, chemicals

• Nuclear area with DNA

• Cell membrane (plasma membrane)—

boundary between cell and environment

Classifying life

Three domains of organisms are now

recognized:

• Bacteria – numerous and diverse

• Archaea – many live in extreme environments

• Eukarya – fungi, algae, protozoa, plants,

animals

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Figure 1.6 Tree of Life

Prokaryotes

Figure 1.7 Drawings of representative microorganisms, as they appear by light microscopy

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Classifying life: Eukaryotes

• We are eukaryotes

• Some are big some are small.

• Hallmarks of eukaryotes:

! Nuclei

! Membrane bound organelles

• Some microbial eukaryotes:

! Yeast

! Fungi

! Protozoa

! Diatoms

Classifying life: Archaea

• Archaea are microorganisms

• No nuclei

• Different than bacteria

! To be discussed later.

• Often live in extreme

environments

• Mostly non-pathogenic

methanoarchaea

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Classifying life: Bacteria

• Bacteria are microorganisms

• Most are harmless

• No nucleus

• Pathogenic:

! Escherichia coli (E. coli)

! Streptococcus (strep throat)

! Yersinia pestis (plague)

! Salmonella (food poison)

• Non-pathogenic:

! Thermus aquaticus (PCR)

! Lactobacillus (dairy products)

! Nitrosomonas (fish aquariums)

Nitrifying bacteria

Let’s define a “microorganism”

• Microorganism:

! Can be eukaryotic, archaeal, or

bacterial.

• Prokaryotes:

! Lack membrane-bound nucleus

! Self replicate

• We will focus is on the Prokaryotes

! Bacteria and Archaea

2 !m

Nucleus

prokaryote

virus

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History of microbiology

• Infectious diseases, population control, and

antiquity.

!Cholera, syphilis, casualties of war, trade.

• Black Death

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History of microbiology

• How did people figure out that

there were microbes?

• Major break through was when

people could see

microorganisms.

• Antony van Leeuwenhoek (1632-

1723)

!Built the first solar light

microscope in 1676.

!Magnification 300X

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Antony van Leeuwenhoek

• “Average” guy with extremecuriosity.

• Excellent eye-sight

• Key player in advancing thefield of microbiology

• He saw the unseen for thefirst time! E.g.:

! Corpuscle

! Bacteria

! Spermatozoa

! Algae

• He reported his observationstoo. In sometimes painfuldetails.

http://www.microscopy-uk.org.uk

Antony van Leeuwenhoek

• First observation of

growing microorganisms.

• Also anaerobic growth

• Experimented with pepper

water in open and sealed

glass tubes.

• Used is microscope to

make is observations.

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• Greek physician Galen said

disease was caused by

imbalance of 4 humours:

! Blood

! Phlegm

! Yellow bile

! Black bile

• Fracastoro: 1478-1553 (Italy)

! Wrote about spread of disease

! Proposed epidemics werespread by tiny “spores”.

Microbes and disease

• Pasteur and Sterilization.

• During the mid 1800’s there

were hints that a transferable

or infectious agent caused

disease.

• Along came Robert Koch

! Showed, without a doubt,

that anthrax was caused

by a bacterium.

www.encyclopedia.com

John Snow and epidemiology

• British epidemiologist around 1850

• Proposed that cholera might come from

water

• Used surveys and maps

• Linked the disease to sewage in water

• Therefore cholera must have come from

sewage.

• Still couldn’t prove that is was a caused

by a microorganism!

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Robert Koch--from modest doctor to pioneering microbiologists

• He was the first to prove that a microbe caused disease.

• In the blood of animals dying of anthrax there was always one typeof bacterium: Bacillus anthracis

• But, did these bacteria cause the disease? Or did something elsecause the disease and then this bacterium came along; takeadvantage of the weakened animal; and grow?

• Supplemental Reading on Web Page from Microbe Hunters

Koch’s Postulates

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Koch’s Postulates: Defined

1. The suspected pathogenic organism should be

present in all cases of the disease and absent from

healthy animals

2. the suspected organism should be grown in pure

culture

3. Cells from a pure culture of the suspected organism

should cause disease in a healthy animal

4. The organism should be re-isolated and shown to be

the same as the original.

Koch’s Postulates: Part II

1. Blood of diseased animal.

2. Injected into healthy animal

3. Found same bacterium in

the blood

4. Repeat

5. What’s the problem:

• How do you know

disease comes from one

bacterium?

• 109 cells/ml.

• Is there only 1 type in

there?

• How do we address thisproblem?

• We need a way to separateindividual bacteria.

• Then we need to culture theisolate and then repeatpostulate #3.

• Solution:

! Dilute sample to one cell

! Use Koch’s method forisolating individual bacteria

! The streak plate

• This was another majoradvancement in the field ofmicrobiology

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The Streak Plate

• Need a solid surface to keep bacteria from

moving away.

!Agar, petri dish

• Means of separating cells.

!Sterile stick or metal loop

• Sterilization method

!Heat

Once all these techniques were developed, Koch wenton to isolate the bacteria that caused Anthrax,Tuberculosis, and Cholera. He received the 1905 NobelPrize for the Tb work

Study Questions:

1. Why was the microscope key to microbiology?

2. What are the 6 characteristics of living cells? Which characteristics are

universal?

3. Which of the 3 Domains contain microorganisms? How do

microorganisms within these domains differ and how are they the

same?

4. What are Koch's postulates and how are they used?

5. What is pure culture, and why is so important for microbiology? What

would be different if Koch didn't start with a pure culture?

6. How did solid media help with obtaining pure cultures?

7. What is sterile technique, and why is it important? In other words,

what would happen if sterile techniques weren't used?