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32 Cards in this Set
- Front
- Back
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Conditions that are important for the growth of bacteria |
-temperature -osmotic pressure -pH -oxygen |
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Not a physical factor that affects bacterial growth |
nutrient concentration |
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nutrient concentration |
growth rate depends on amounts of nutrients in the environment
-one key nutrient(in lowest amount) will determine how much growth can occur over time) |
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limiting factor in nutrient concetration |
lowest amount nutrient that determines how much growth over time |
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physical factors and bacterial growth |
-temperature -pathogens -hydrostatic pressure -osmotic pressure -pH |
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temperature responses of microbes: psychrophile and types |
grows at: 5dC facultative: max at 20dC or above obligate: max below 20dG |
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Mesophile temp response |
grows at 37 |
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Thermophile temp growth and types |
-grows at 50-70dC eurythermophile-broad range of temp; can grow at 37dC -stenothermophile-narrow range of temp; cannot grow at 37dC |
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hyperthermophile |
>70C |
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human pathogens and type |
optimum temp varies for 20-45dC -eurythermophile |
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Phys factor:hydrostatic pressure and barophiles |
barophiles grow faster at pressure over 1 atm - some grow at bottom of the ocean, at extremely high pressure |
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Phys factor: osmotic pressure |
-some extremeophiles can grow at [salt]>5M NaCL |
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hypotonic solution |
net water gain -low salt concentration -water moves into cell -causes cell to swell -cell wall will lyse |
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hypertonic solution |
net water loss -high [salt] -water moves out of cell, cell will shrink |
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isotonic solution |
extracellular and intracellular salinities(indicated by blue spheres) are similar, there is no net movement of water across the membrane |
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acidophiles |
ph=.1-5.4 ex. lactobacillus acidophilus |
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neutrophile |
ph-5.4-8.0 -most of disease causing bacteria |
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alkaliphiles |
pH7.0-11.5 vibrio cholera, alcaligenes faecalis -bacteria can compensate somewhat for external pH by pumping protons out of the cell |
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what most pathogens are |
neutrophiles(5.5-8) |
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helicobacter pylori |
-can cause gastric ulcers -acid tolerant -secretes bicarbonate and urease |
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vibrio cholerae |
can thrive at ph=9 |
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Oxygen and bacterial growth |
metabolism of oxygen forms 2 highly toxic compounds, H202 and superoxide(o2-), which are broken down by catalase and superoxide dismutase |
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catalase |
breaks down h202 |
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superoxide dismutase |
breaks down O2- |
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table 6.7 aerobe |
synonyn: strict aerobe growth in air:yes growth w/o O:no possession of catalase and superoxide dismutase:Yes description: requires O; cannot ferment Ex. mycobacterium tuberculosis, pseudomonas aeruginosa, bacillus subtilis |
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anaerobe |
syn:strict anaeroble grow in air:no grow without O: yes enzymes:no description:killed by O, ferments in abs of O2 Ex: clostridium botulinum, bacteroides melaninogenicus |
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facultative |
grow in air:yes grow without O: yes enzymes:yes description: respires with O2, ferments or uses anaerobic respiration in absence of O2 Ex. e.coli, shigella dysenteriae, staph aureus |
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indifferent |
syn: aerotolerant anaerobe grow in air: yes w/o O: yes enzyme: yes description: ferments in presence or absence of O2 ex: steptococcus pneumoniae, strep pyogenes |
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microaerophilic |
grow in air: slight grow without o: yes enzyme: small amounts description: grows best at low O2, can grow without O2 ex: campylobacter jejuni |
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how they are in tubes |
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anaerobic culture system |
a simple sealed container, an anaerobic jar, can be used for cultivating anaerobic microorganisms on agar plates. chemical reactions within the jar conusme virtually all of the O2, creating an anoxic environment |
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capnophilic |
prefers increased CO2(neisseria spp) |
