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microorganisms
- a diverse group of organisms that exist as free-living single cells or cell clusters
- single cell can live outside of other cells
- includes algae/fungi/protist, bacteria, archaea
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Robert Hooke
- built compound microscope
- saw and documented microorganisms
- coined the term cells from viewing cork
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Anton van Leeuwenhoek
- had simple better lens with better magnification
- first recorded observation of bacteria
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Louis Pasteur
- disproved spontaneous generation with swan-neck flask experiment - showed microbes come only from pre-existing microbes
- studied fermentations and isolated microorganisms responsible for fermentations
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swan neck flask experiment
- nonsterile liquid put in flask, neck drawn out, sterilize
- MO trapped in bend, remained sterile for years
- flask tipped, MO grow in culture
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Pasteur's fermentation observations
- need specific microbes for specific fermentation
- complex organic compounds present
- some compounds present were stereospecific
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Robert Koch
pioneered pure cultures on solid medium to grow individual colonies
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Semmelweiss, Pasteur, Lister
- came up with germ theory in response to miasma theory
- encouraged antiseptic practices - washing hands/instruments to prevent spread of germs
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Koch's postulates
- established framework for showing that a disease is caused by a microorganism
- 1) the suspected organism should be present in all cases of disease and absent from healthy individuals
- 2) the suspected organism should be isolated form a diseased individual and grown in pure culture
- 3) organisms from pure culture should cause disease in healthy individual
- 4) organism should be reisolated and shown to be same as original
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cases that do not satisfy Koch's postulates
- disease caused by microbe that is present in normal individuals
- organism can't be grown in culture
- no animal model
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Martinus Beijernick
- enrichment culture
- selective culture medium favor growth of specific organisms
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Beijernick and Winogradsky
- idea of microorganisms as biogeochemical agents
- isolated bacteria with specific properties using enrichment cultures
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autotrophs
acquire carbon from air
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chemolithotrophs
gain energy from oxidation of inorganic compounds
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nitrogen fixing bacteria
convert N2 in the air to to NH3, which can be used
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bacteria and metabolism
- bacteria have far greater metabolic diversity
- can live on earth without plants and animals, reverse not true
- nitrogen cycle depends on bacteria - perform nitrogen fixation and nitrification
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