Micro Ch. 6
|Metabolic Cell Needs|| C, N, O, H = 95% of dry weight of cell. Also, has H2O.|
Trace elements like Zn.
H most common, needed for H-bonds and e-transfer.
|Oxygen Requirements||O2 essential for obligate aerobes due to final electron acceptor in transport chain.|
Obligate anaerobes: O2 will kill them. Susceptible to H2O2 toxicity.
Facultative anaerobes: use a bit of O2. O2 not final electron acceptor, uses fermentation pathway. Most aerobes are facultative anaerobes.
Aerotolerant anaerobes - don't use O2.
Microaerophiles - require 2-10% O2.
|biofilms|| m.o. communities aka slime.|
cell to cell chemical communication aka quorum sensing allow m.o. to coordinate activity.
|*4 toxic forms of Oxygen|| 1)singlet: 'O2 (very reactive) used by macrophages|
2)superoxide radical: O2- aerobes produce superoxide dismutase to detoxify, anaerobes are killed.
3)peroxide anion ([O−O]2-) highly reactive, makes hydrogen peroxide a good antimicrobial agent. deep wounds (against anaerobes)
4)hydroxyl radical (OH) MOST REACTIVE
|Oxygen Enzymes Reactions|| catalase 2 (H2O2) -> 2H2O + O2 (bubbles)|
peroxidase H2O2 + 2H+ -> 2H2O (no bubbles)
superoxide dismutase O2- + O2- + 2H+ -> 2H2O2 + O2
|Oxygen Enzymes Function|| catalase: breaks down hydrogen peroxide into water and oxygen, hence bubbles.|
peroxidase: breaks down hydrogen peroxide into water
superoxide dismutase: takes two superoxide radical and converts to hydrogen peroxide (which needs to be broken down) and hydrogen
|Enzymes Aerobes have|| Catalase to detoxify peroxide anion.|
SOD to detoxify superoxide radical.
|Trace Elements that M.O. need||Zn, Fe, Cu, Mo. Cofactors for enzymes.|
|M.O. Physical Requirements|| Temperature|
|*Temperature|| Min Temp: Lowest temp where metabolism possible, very slow.|
Optimal Temp: greatest amt of metabolism
Max Temp: Temp below perm. protein denaturation.
|*M.O. Temp. Groups|| Psychrophiles (likes cold) best at 15C, die at >20C|
Mesophiles best at 20-40C includes pathogens
Thermophiles best at >45C
Hyperthermophiles grow at >80C
|*pH Groups|| Neutrophiles (inclusive of pathogens) best at 6.5-7.5.|
Acidophiles (e.g. lactobacillus) 3.5. If gone, Candida yeast takes over. Also, Helicobacter pylori, a neutrophile, gram - rod, neutralizes stomach acid urease, makes bicarbonate from urea.
Alkalinophiles best in H2O @ 9.0pH. e.g. Vibrio cholerae, gram- rod. likes sewage.
|Osmolarity and bacteria|| hypotonic solution: lyse|
hypertonic solution: plasmolysis or shrink
|halophile||salt loving. tolerate up to 20% salt. S. aureus and S. epi, skin is salty.|
|Bacteria and Media General|| grow on any media, non-fastidious, e. coli?|
fastidious bacteria, pathogens need special nutrients like SBA 5%
|Culture Media Types|| Complex: general, often with SBA added|
Selective: has nutrients favoring some M.O. inhibiting others
Differential: shows visible changes in media or colonies
|Generation Time|| Doubling time - time required for M.O. cell to grow & divide = period between 'birth' & prod. of offspring.|
[from book]: the time required for a cell to divide and population to double.
|Microbial population growth|| lag: adjusts to env; no repro; make enzymes|
log: lots of growth&metabolism. No cell death.
stationary: nutrients depleted, wastes accumulate, death causes growth rate to flatline.
death: no new nutrients have been added, death rate overcomes growth rate. spores produced.