LG5.8 growth of bacteria Flashcards
what’s a colony?
population of cells arising from a single cell or endospore, or from a group of attached cells
define obligate aerobe.
-uses only aerobic respiration
-requires O2 to live have both SOD and catalase E.g. Mycobacterium tuberculosis
define facultative anaerobe
-‘F’ for ‘F’lexible - can live with O2 and without ( prefers O2 though) -have both SOD and catalase -E.g. Escherichia coli
define microaerophile
-damaged by normal atm. levels O2 (20%), -needs 2-10% -usually have SOD and catalase in very low concentrations -can be in stomach in humans -E.g. Helicobacter pylori
define obligate/strict anaerobe
-cannot live with O2 around -usually lack both SOD and catalase -can be in colon and parts of mouth in humans -E.g. Clostridium
define aerotolerant anaerobe
- ignores O2 - grows the same no matter how much or little O2 -usually have SOD and lack catalase E.g. Propionibacterium acnes
- uses anaerobic resp or fermentation - these doN’T have system for aerobic resp
define pure culture
-contains only one species or strain, ID aided by characteristic colony color, shape, texture, size
give unbalanced equation for superoxide dismutase (SOD)
2O2- + 2H+ → O2 + H2O2
(Superoxide [2O2-]is toxic)
give unbalanced equation for catalase
2H2O2 → 2H2O + O2
(hydrogen peroxide [2H2O2] is toxic)
describe enriched growth media and recognize growth requirements of fastidious bacteria and intracellular bacteria
-complex media + addition of sterols, blood, serum, egg yolk, -E.g…. -sheep blood agar (most clinically impt. Gr+, Gr-) -chocolate (heated, lysed blood) agar (fastidious e.g. Neisseria gonorrhoeae, Haemophilus influenzae)
describe selective growth media.
- media contains ingredients that inhibit growth of some organisms but allow others to grow
- E.g. mannitol salt agar (MSA) (high concentration NaCl (7.5%))
- MSA inhibits growth of most organisms but permits staphylococci to grow
describe differential growth media
-contains ingredients that allow groups of microorganisms to be visually distinguished by appearance of colony or surrounding media, usually on basis of some biochemical difference between the two groups
what is complex media?
- “has lots of stuff in it”
- supports growth for a wide variety bacteria, E.g. nutrient agar
describe mannitol salt agar (MSA)
- media has mannitol AND pH indicator
- inhibits most pathogens except Staphylococcus - (example of organism that can tolerate high salt environment) –> makes this media SELECTIVE
- this is DIFFERENTIAL because mannitol lets you distinguish between organisms than can and cannot metabolize mannitol to an acidic product (auerus, epidermidis)
describe MacConkey agar
-selective AND differential
contains bile salts, dye crystal violet
- inhibits growth of Gr+ bacteria and SELECTS for Gr- bacteria (but not fastidious Gr-)
- also lactose and pH indicator (allows DIFFERENTIATION of Gr- bacteria based on their ability to ferment lactose) (lactose fermenters → acid end-products → react with colorless pH indicator → red/pink color)
what makes an organism fastidious?
when the organism requires many macro- and micronutrients.
Sketch and label a bacterial growth curve.
What happens during lag phase?
cells synthesizing new macromolecules including DNA - preparing for replication in lag
What hapens during log phase?
-cells growing and dividing at maximal rate possible given their genetic potential and the local environment
–dividing and doubling at regular intervals
What happens during stationary phase?
–total number viable cells remains constant
–nutrient limitation, accumulation of toxic wastes, depletion of O2
–endospore formation
–secondary metabolite synthesis, e.g. toxins, antibiotics
What happens during death phase?
decrease in number viable cells, often exponential
What are the 3 interconnected pathways of cellular respiration?
What’s the ATP yield for prokaryotes? Eukaryotes?
- glycolysis
- krebs cycle
- ETC
- Glucose is completely oxidized to CO2 and H2O in Pro and Eu
- 38 and 36
O2 is final electron acceptor in Pros and Eus
Give a few details of prokaryotic anaerobic respiration.
- inorganic compounds other than O2 serve as final electron acceptors (e.g. nitrate)
- used by obligate anaerobe, faculative anaerobes, aerotolerant anaerobes
- yields less energy than aerobic respiration ( between 2 and 37 ATP) [glycolysis used along with only part of the Krebs cycle and part of the E.T.C.]
these grow faster than fermentation bacteria but slower than aerobic
Give some details of fermentation.
- any metabolic process that releases energy from a sugar or other organic molecule, does not require O2 (but can occur in the presence O2) or an electron transport system, and uses an organic molecule as the final electron acceptor (ATP only generated in glycolysis–does not use Krebs cycle or E.T.C.)
- used by obligate anaerobes, facultative anaerobes, aerotolerant anaerobe
- most anaerobic bacteria of medical importance use fermentation as the main mode of energy generation!!
- produces only 1 or 2 ATPs per starting molecule (most energy from starting material remains in bonds of organic end products…i.e. not completely oxidized
- these grow slowest
- products used in I.D. (alcohol, gas, acid)
