Microbial Genetics Flashcards
Lucretius and Fracastoro
thought that disease was caused by invisible living creatures
Stelluti
first saw microorganisms using a microscope supplied by Galileo
Hooke
published first drawings of microorganisms
Van Leeuwenhoek
developed even better microscopes. His achieved magnification of 50-300x.
Observed and drew bacteria from dental plaque
What is spontaneous generation?
The belief that living organisms could develop from non-living matter
Redi
Challenged spontaneous generation with his wokr using meat, flies and maggots
Needham
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
Spallanzani
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
The investigators who challenged the claim that heating air in sealed flasks destroyed its ability to support life showed that
no growth occurred in sterile medium after exposure to heated air (in non-sealed flasks) or filtered (but not heated) air
Who settled the matter of spontaneous generation?
Louis Pasteur
What did Pasteur’s swan-neck flask experiment do and show?
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.
Who was the first industrial microbiologist or biotechnologist
Pasteur, he showed that yeast fermented sugar in grape juice to produce alcohol but the presence of bacteria produced unwanted acid
What laid a practical basis for the Germ Theory of Disease?
Pasteur’s wine experiment
Even after Pasteur disproved spontaneous generation, what did people still believe?
That infectious disease was spread by poisonous vapours called miasmas. Another theory involved an imbalance of the 4 humours of the body
Which 3 people directly supported the germ theory of disease?
Bassi - silkworm disease caused by fungal infection
Berkely - irish potato blight caused by mould
de Bary - cereal crop blights caused by fungus
Which 3 people indirectly supported the germ theory of disease?
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
Who developed basic microbiological cultivation techniques?
Koch and co-workers. Used agar and petri dishes - produced pure cultures - essential
Whose work verified the Germ theory of disease?
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
What are Koch’s 4 postulates?
- Microbe must be present in every case but absent from healthy organisms
- Suspected microbe must be isolated and grown in a pure culture
- Same disease must result when inoculated into a healthy host
- Same microbe must be isolated again from disease host
Why are Koch’s postulates not always feasible?
- Some pathogens are part of normal microbiota
- Some pathogens cannot be grown/cultured
- Some pathogens grow/cause disease only in humans
- Sometimes more than one pathogen is involved in a disease
What are Koch’s 4 molecular postulates and what do they emphasise?
They focus on the virulence genes rather than the microbe itself.
- VG must be found in pathogenic stains
- VG must be expressed during infection/disease
- Mutation or deletion of VG decreases pathogenicity
- Replacement/restoration of VG mutation/deletion restore pathogenicity
