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microbial growth
the numbers to cells not to the changes in the size of the cells
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colonies
accumulations of the cells large enough to be visible without a microscop
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requirements for growth
- physical - temperature, pH, osmotic pressure
- chemical - carbon, oxygen, sulfur, nitrogen
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chemically defined media
media infused with certain chemicals to accommodate certain bacteria
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fastidious
many growth factors required
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complex media
used to grow most heterotrophic microbes
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anaerobic growth media
often has thio (sulfur) chemicals
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selective media
suppresses growth of unwanted bacteria
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differential media
distinguish between types of bacteria
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lyophilization
dehydrated / freeze dried bacteria
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generation time
time needed to undergo binary fission
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lag phase
phase where bacteria is gathering materials; preparing for division; some division
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log phase
phase where there is rapid division
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stationary phase
phase where rate of reproduction = rate of death
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death / decline
rapid death of the bacteria
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direct counts
- count colonies
- quebec colony counter
- serial dilutions
- direct microscopic counts
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count colonies
assume that 1 bacteria formed the colony (CFU = colony forming unit)
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quebec colony counter
count typical amount of colonies in the appropriate size box and multiply by the number of boxes that fit the plate
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serial dilutions
- decrease concentration to be able to do direct count
- must multiply colonies by dilution number
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direct microscopic counts
put colonies in liquid on a microscope slide
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indirect counts
- spectrophotometer
- metabolic products
- dry weight
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spectrophotometer
- measures absorbency or transmission (turbidity)
- turbidity is caused by bacteria
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metabolic products
determine how much bacteria by knowing how much of a product is produced by 1 bacteria
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dry weight
dry bacteria up and weigh
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mesophile
middle temperature loving
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thermophile
heating loving bacteria
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plasmolysis
cell shrivels
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