Prokaryotic Biology Lecture 2/Chapter 1

improved continuously

Light microscope invented in 1600s, quality __________

small eukaryotes (eukaryotic cells)

mid-1600s: Robert Hooke observed ____________________

bacteria (prokaryotic cells)

1676: van Leeuwenhoek discovered ____________

Biogenesis

Living organisms arise from preexisting life

spontaneous generation

The alternative hypothesis is __________________—that living organisms can arise from non-living matter

Redi

1688: ______ shows that flies do not spontaneously

generate and therefore disproved spontaneous generation

John Needham

– Even after Redi’s experiments disproved spontaneous

generation for flies, many people thought that microbes

were an exception.

– _______________ (1745)put boiled nutrient broth into a sealed flask

Spallanzani

__________ (1765)—placed nutrient broth in a flask, sealed it and sterilized it by boiling—no microbes grew

– This same scientist argued that this disproved spontaneous generation for microbes

spontaneous generation for microbes

– Pasteur performed a brilliant experiment (1861):

• S-shaped flasks kept microbial contaminants out, but let air in

• Pasteur demonstrated that microorganisms are present in the air, and contaminate the broth when the flask is open and they fall in.

This finally disproved ____________________________

• Disapproval of spontaneous generation.

• Microbes cause fermentation.

• Early vaccine development.

• Pasteurization

Louis Pasteur

viruses, bacteria, fungi, or protozoa

Disease-causing organisms, what we usually mean when we

say “germs”, are ______, _______, _______, and __________

Archaea

no _________ have been demonstrated to cause human disease

• Rabies—transmitted to new host when bitten by an infected animal

• Anthrax—in the 1800’s people knew it was possible to

catch this from cattle

• Battlefield infections--significance of infection in warfare

was 1st recognized by the British nurse Florence

Nightingale (1820–1910)

• Wound sepsis—Lister found that sterilization of surgical

instruments reduced wound sepsis, gangrene, death

4 supporting observations of Germ-Theory

sterilization

pasteurization is not the same as ____________

Koch’s Postulates

• Provides means of testing hypothesis:

– “Does this germ cause that disease?”

– Causality?

• Organism must meet 4 criteria:

– 1. Microbe always present in diseased

• Absent in healthy

– 2. Microbe is grown in pure culture

• No contamination of other microbes.

– 3. Introduce pure microbe into healthy individual

• Individual becomes sick (same disease)

– 4. Same microbe re-isolated from now-sick individual

4 of Koch’s Postulates

• Some organisms cannot be grown in pure culture.

• Using humans in completing the postulates is

unethical (no animal model).

• Cofactors are needed for disease development

(ubiquitous pathogens, not every infected one

develops disease).

• Some diseases develop extremely slow.

• Molecular and genetic evidence may replace and

overcome these limits

Limitations of Koch’s Postulates

MEMORIZE THIS CHART

Ignaz Semmelweis (1818-65)

discovered handwashing

Joseph Lister (1827-1912)

started Antiseptic surgery

Alexander Fleming

1929-1941: Penicillin

Variolation

powdered smallpox scabs were blown up the noses of healthy

-used by Turkish physicians, Lady Montagu, Edward

Jenner

– Black death/plague in Europe

– Smallpox in Americas

2 examples of microbial diseases change history

– Diseases destroying crops (Irish famine)

– Control of microbial growth to preserve food

– Fermentation in food/beverage production

• bread, wine, cheese

• Chocolate!

Examples of microbes affect food availability

plants and animals

Microbes lived before ______ and _______