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44 Cards in this Set
- Front
- Back
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microbial growth
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increase in population of microbes, not increase in size
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binary fission
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cell elongates & dna replicated
cell walland plasma membrane begin to grow inward cross-wall forms completely around divided dna cells separate |
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generation time
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time required for cell to divide
1-3 hrs for most |
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phases of growth
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lag
log stationary death phase |
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lag phase
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1hr to days
# cells change little b/c don't immed reproduce in new medium intense metabolic activity |
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log phase
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cells divide; growth & logarithmic increase
cellular reproduction most active |
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stationary phase
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growth rate slows
microbial death = # new cells exhaustion of nutrients |
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death phase
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incr death decr growth
pop diministed sometimes morph during this phase |
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growth temps
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psychophiles
mesophiles thermophiles |
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psychophiles
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cold loving
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mesophiles
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moderate T
most common |
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thermophiles
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heat loving
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minimum growth temp
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lowest temp species can grow
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optimal temp
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T species grow best
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pH
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most grow b/w 6.5 and 7.5
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hypertonic
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soln higher [ ] than microb cell
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plasmolysis
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shrinkage of cytoplasm due to hypertonic soln
water moves out |
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carbon
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E source; most impt for growth besides water
1/2 dry weight bacteria cell is C |
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nitrogen
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AA & pro
bacteria decompose pro & use AA 14% dry weight |
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sulfur
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AA thiamine, biotin
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phosphorus
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dna
rna atp membranes |
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trace elements
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usually enzyme cofactors
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toxic oxygen
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pathogens killed by exposure
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singlet o2
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extrememly reactive
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superoxide free radicals o2-
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toxic, bubbles w/ catalase; not / peroxide
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peroxide anion o2 2-
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toxic
bubbles w/ catalase not with peroxidase |
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hydroxyl radical OH-
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most reactive
formed in cytoplasm by ionizing radiation most aerobic respiration produce trace amts |
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measure microbial growth
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plate count
turbidity (cloudy) |
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culture medium
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nutrients prepared for microbial growth
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sterile
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no living microbes
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inoculum
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introduction of microbes into medium
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culture
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microbes growing in /on culture medium
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to grow a culture
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right nutrients for MO
moisture adjusted pH level of O2 incubated @ proper temp |
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agar
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complete polysaccharide
plates, slants, deeps |
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culture media
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chemically defined media: exact nutrient composition known
complex media: extracts and digests of yeasts, meat, plants |
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anaerobic culture methods
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anaerobic jar
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differential media
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easy to distinguish colonies; suppress unwanted microbes & encourage desired growth
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blood agar
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used to identify bacterial species that destroy RBC
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mannitol salt agar
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discourage growth of competing organisms
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enrichment culture
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for low levels of microbe to increase # and culture bacteria
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pure culture
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only one species or strain
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colony
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population of cells arising from single cell or spore
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streak plate method
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used to isolate pure cultures
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deep feezing
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pure culture of microbes placed in suspending liquid and quick frozen
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