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PART II Pathways of PART II Pathways of Discovery in MicrobiologyDiscovery in Microbiology

The Historical Roots of The Historical Roots of MicrobiologyMicrobiology

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Anton van Leeuwenhoek and his

animalcules

Biogenesis vs Spontaneousgeneration

Germ Theory of Fermentation

Germ Theory of disease and

Kochµs Postulates

Immunization

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Robert Hooke (1665) - observed that plant material wascomposed of little boxes, he introduced the term ³ cell.´

Cell walls in cork tissueCell walls in cork tissue

Robert Hook and the developmentof the cell theory

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The first microscopic descriptions of microorganismsby Robert Hooke

blue mold growing on the surface of leather (round structures contain spores of the mold)

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the first to describe bacteria.A haberdasher Made >250 microscopes

Anton van Leeuwenhoek (1673)Anton van Leeuwenhoek (1673)

His insatiable curiosity about the natural world and his detaileddescriptions of what he saw that made him one of the founders of Microbiology«

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Simple microscope

Leeuwenhoek¶s drawingsof bacteria.

The animalcules«.

bacteria and protozoa

He found Ä animals appearing tome ten thousand times less thanthose which maybe perceived in

the water with the naked eye³

ÄIn the said matter, there weremany very little animalcules, very prettily a-moving...More over, the

other animalcules were in suchenormous numbers, that all the

water...seemed to be alive³

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Spontaneous generation (Abiogenesis)VS

Biogenesis

F rogs and worms arose spontaneously from ponds

living organisms could arise from non-living or decomposing matter.

Ancient Myths/ Spontaneous Generation

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Francesco Redi (1668)Francesco Redi (1668)--demonstrated that maggots appear on decayingdemonstrated that maggots appear on decayingmeat only when flies are able to lay eggs on the meat.meat only when flies are able to lay eggs on the meat.

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J ohn Needham (1745) revived theory of spontaneous generation at the microorganismlevel«.cooked meat will give rise to mirobes!!!

Anti-spontaneous generation

Lazaro Spallanzi ± boiled beef extracts in a flask (1hr) then sealed it.Microbes did not grow.......

Pro-spontaneous generation

J ohn Needham ± air is needed for spontaneous generation

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After 100 years..........

(1815-1873)

(1854)

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Felix Pouchet (1859)

-a french naturalist claimed to have carriedout experimentt conclusively proving thatmicrobial growth could occur without air contamination...

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-a French chemist

-yeast ferment sugars to alcohol

-high or low quality wine is dependenton the type of microbe/yeast

-bacteria can oxidize the alcohol toacetic acid.

-develop pasteurization

Louis Pasteur (1802-1895) and theGerm theory of Fermentation

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If fermentation products from grape juice

is the work of microorganisms«.thenmeat or broth putrefaction could be theresult of microbial contamination «

Louis Pasteur (1802-1895) and the

End of Spontaneous Generation Controversy

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Pasteurµs experiment

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The Link to the Germ theory of Disease

Pasteur saving the silk industry«..- proved that protozoans caused the silkworm disease- control the disease by raising caterpillars from eggs produced

by healthy moths

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The Link to the Germ theory of Disease

J oseph Lister (1860)

- father of modern surgery

- introduced the use of disinfectant to clean surgicalwounds in order to control

infections in humans

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Germ theory of Disease and Robert Koch

Robert Koch (1843 -1910)

- lifelong professional rival of Louis Pasteur

-a german physician

- isolated the bacterium that causes Anthrax... adisease decimating the herds of cattle and sheep in

Europe

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Robert Koch and thedevelopment of Laboratory

techniques

Initially used sterile surface of cut/sliced boiled broth

Used gelatin in solidifying regular nutrient medium

Kochµs assistant suggested the use of agar

Richard Petri developed the petri dish

Tuberculosis ±Mycobacterium tuberculosis

Cholera- Vibrio choleraTyphoid fever - Salmonella typhi

Diptheria - Corynebacterium diptheriae

Tetanus - Clostridium tetani

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Pasteur and the Road toVaccination

Experiment 1: Pasteur injected healthy chickens with purecultures of cholera bacteria

Experiment 2.

Chickens in experiment 1 Uninoculated chicken

Young culture of cholera bacteria

injected

Remained alive andhealthy

Chickens died

Results - chickens did not get sick

Explanation - the inoculum used was several weeks old

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Pasteur called the avirulent cultures vaccine (fromlatin vacca = cow ) in recognition of the earlier work of Edward Jenner

Edward J enner vaccination(1798)

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Cowpox virus

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Pasteur also developed the rabies vaccine...

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Microbial Diversity and the Rise of GeneralMicrobial Diversity and the Rise of GeneralMicrobiologyMicrobiology

Beijerinck and Winogradsky-studied bacteria in soil and water and developed theenrichment culture technique for the isolation of representatives of various physiological groups:

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Ferdinand Cohn founded the field of bacteriologyand discovered bacterial endospores

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Martinus Beijerinck (1851-1931)

The concept of enrichment culture technique

Isolated the first pure cultures of many soiland aquatic microorganisms.

- aerobic nitrogen fixing bacteria

-sulfate reducing bacteria

- root nodule bacteria

- L actobacillus species

- green algae

- basic tenets of virology

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- chemolithotrophy/chemoautotrophy

- nitrogen fixation.

Winogradsky

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Landmarks in Microbiology

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The Modern Era of The Modern Era of MicrobiologyMicrobiologyI n the middle to latter part of the twentieth

century, basic and applied microbiologyworked hand in hand to usher in the currentera of molecular microbiology. Figur e 1.17depicts some of the landmarks inmicrobiology in the past 65 years.

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Major new concepts in microbiologyemerged during this period, includingenrichment cultures

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S ome subdisciplines of applied

microbiology include medical microbiology,immunology, agricultural microbiology,industrial microbiology, aquaticmicrobiology, marine microbiology, andmicrobial ecology.

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S ome subdisciplines of basic microbiologyinclude microbial systematics, microbial physiology, cytology, microbial biochemistry, bacterial genetics, and molecular biology.

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- claimed that microorganisms could arise spontaneously from heated nutrient broth

-he demonstrated that inoculation witcowpox material provides humans wiimmunity to smallpox.

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S ugar converts to alcohol and lots of gas

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R obert Koch developed a set of postulatesto prove that a specific microorganism causesa specific disease:

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1 . The suspected pathogenic organismshould be present in all cases of thedisease and absent from healthy animals.

2. The suspected organism should be grownin p ur e c u lt ur e ²that is, a culture

containing a single kind of microorganism.

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3 . Cells from a pure culture of the suspectedorganism should cause disease in ahealthy animal.

4. The organism should be reisolated and

shown to be the same as the original.

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The Father of Modern S urgery

micro 200 lec 2

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