Microbial Genetics

Question 1

Lucretius and Fracastoro

Answer 1

thought that disease was caused by invisible living creatures

Question 2

Stelluti

Answer 2

first saw microorganisms using a microscope supplied by Galileo

Question 3

Hooke

Answer 3

published first drawings of microorganisms

Question 4

Van Leeuwenhoek

Answer 4

developed even better microscopes. His achieved magnification of 50-300x.
Observed and drew bacteria from dental plaque

Question 5

What is spontaneous generation?

Answer 5

The belief that living organisms could develop from non-living matter

Question 6

Redi

Answer 6

Challenged spontaneous generation with his wokr using meat, flies and maggots

Question 7

Needham

Answer 7

Supported spontaneous generation by showing that life developed in lightly boiled meat broths, sealed AFTER heating. He proposed that organic matter contained vital force that could confer life on non-living matter

Question 8

Spallanzani

Answer 8

Challenged spontaneous generation. Showed that no life developed in strongly boiled broths sealed BEFORE heating, as long as they remained sealed. He proposed that air carried living microorganisms but that these organisms might also need external air to grow

Question 9

The investigators who challenged the claim that heating air in sealed flasks destroyed its ability to support life showed that

Answer 9

no growth occurred in sterile medium after exposure to heated air (in non-sealed flasks) or filtered (but not heated) air

Question 10

Who settled the matter of spontaneous generation?

Answer 10

Louis Pasteur

Question 11

What did Pasteur’s swan-neck flask experiment do and show?

Answer 11

Showed that air contained microbes capable of growth.
Flasks of broth with swan necks were boiled to destroy microbes –> sterile. Flasks were not sealed Swan neck intact: no life developed, microbes trapped at base and broth is sterile. Swan neck broken: growth occurs, microbes can get in.

Question 12

Who was the first industrial microbiologist or biotechnologist

Answer 12

Pasteur, he showed that yeast fermented sugar in grape juice to produce alcohol but the presence of bacteria produced unwanted acid

Question 13

What laid a practical basis for the Germ Theory of Disease?

Answer 13

Pasteur’s wine experiment

Question 14

Even after Pasteur disproved spontaneous generation, what did people still believe?

Answer 14

That infectious disease was spread by poisonous vapours called miasmas. Another theory involved an imbalance of the 4 humours of the body

Question 15

Which 3 people directly supported the germ theory of disease?

Answer 15

Bassi - silkworm disease caused by fungal infection
Berkely - irish potato blight caused by mould
de Bary - cereal crop blights caused by fungus

Question 16

Which 3 people indirectly supported the germ theory of disease?

Answer 16

Semmelweiss - noted increase death from peurperal fever in delivering women treated by students/physicians rather than midwives
Snow - cholera correlated with water from certain sources
Lister - heat sterilisation and phenol used to reduce surgical infections

Question 17

Who developed basic microbiological cultivation techniques?

Answer 17

Koch and co-workers. Used agar and petri dishes - produced pure cultures - essential

Question 18

Whose work verified the Germ theory of disease?

Answer 18

Koch’s work showing bacillus anthracis caused anthrax. He found bacillus anthracis in cattle which died of anthrax - grew it in a drop of aqueous humour and showed that the cell he grew could cause anthrax in mice - independently confirmed by Pasteur

Question 19

What are Koch’s 4 postulates?

Answer 19

1. Microbe must be present in every case but absent from healthy organisms
2. Suspected microbe must be isolated and grown in a pure culture
3. Same disease must result when inoculated into a healthy host
4. Same microbe must be isolated again from disease host

Question 20

Why are Koch’s postulates not always feasible?

Answer 20

1. Some pathogens are part of normal microbiota
2. Some pathogens cannot be grown/cultured
3. Some pathogens grow/cause disease only in humans
4. Sometimes more than one pathogen is involved in a disease

Question 21

What are Koch’s 4 molecular postulates and what do they emphasise?

Answer 21

They focus on the virulence genes rather than the microbe itself.

1. VG must be found in pathogenic stains
2. VG must be expressed during infection/disease
3. Mutation or deletion of VG decreases pathogenicity
4. Replacement/restoration of VG mutation/deletion restore pathogenicity