2_Bacteriology II Flashcards
bacterial growth phases
- lag = before cells start to grow – can mimic adaptation to a new body site
- log = exponential growth – can mimic rapid or slow growth in the host but results in increased bacterial numbers
- stationary
types of “stationary” phase in the bacterial growth cycle
- stationary
- survival = balanced slow growth in a subpopulation (no net gain in numbers)
- death = culture slowly dies out
- cells in stationary phase can be hypermutable and accumulate mutations
binary fission:
define
growth of bacteria into 2 equal daughter cells
exponential growth typically reflects the…
binary fission of bacteria
doubling time (generation time) of the culture:
define
time it takes for the number of cells to increase by a factor of 2
what factors slow bacterial growth in a host?
- nutrient availability
- competition (bacterial cell density)
- build up of toxic byproducts
- immune system
how do bacteria convert glucose to pyruvate?
- use the Embden-Meyerhof-Parnas pathway
describe the Embden-Meyerhof-Parnas pathway:
key features
- 2 high energy phosphates are consumed:
- ATP
- high energy phosphate PTS system – group translocation
- 4 ATP are produced.
- NADH+H+ is produced and must be oxidized by either reduction of pyruvate (fermentation/oxidation) or by being used in an electron transport system (respiration).
In addition to glucose, what are some alternative sugars that can be used by bacteria to produce ATP?
- hexoses
- complex sugars
- citrate
what are possible endproducts from fermentation?
- acids
- lactic acid, butyric acid
- alcohols
- ethanol, 2,3-butanediol
- gas
- CO2
what other substrate can bacteria use for respiration?
NADH+H+
Overview of Respiration in bacteria:
process and outputs
Bacteria that respire transform pyruvate –> acetyl-CoA –> break down to CO2.
This provides bacteria with:
- NADPH for biosynthesis
- additional molecules of NADH+H+ for use in generating a proton motive force
- FADH+H+ that can also be used for the generation of a proton motive force
proton motive force:
define
produced by passing the electrons from NADH+H+ to a series of electron carriers that use the excess energy to pump protons (H+) outside the cell.
carriers of the proton motive force
- cytochromes
- quinones
- flavoproteins (Fe-S proteins)
final electron acceptor(s) of the proton motive force
- acceptor can be O2 (aerobic respiration, oxidative phosphorylation) or
- other inorganic compounds (anaerobic respiration).
how does proton motive force generate ATP?
- This creates a membrane potential and a pH gradient.
- The re-internalization of the protons through F0/F1 ATPase ATP synthase is used to:
- produce ATP
- transport small molecules/ions
- power flagella for motility
how do bacteria that use fermentation only differ?
can run the ATPase pump backwards, using ATP to pump protons out of the cell and charge the membrane.
what are the physical requirements for bacterial growth?
- pH – most pathogens are neutrophiles or acidophiles
- salt concentration – most pathogens are non-halophillic or halotolerant
- temperature – most pathogens are mesophils although cold-tolerant bacteria and psychophiles are important in food spoilage
define the following growth requirements:
- anaerobe
- strict anaerobe
- aerotolerant anaerobe
- anaerobe = grows without O2
- strict anaerobe = killed by O2
- aerotolerant anaerobe = withstands O2
define the following growth requirements:
- microaerophilic
- aerobe
- obligate aerobe
- facultative
- microaerophillic prefers reduced O2 tension for growth
- aerobe = growths only with oxygen
- obligate aerobe only uses O2 as a terminal electron acceptor, must have oxygen
- facultative = can grow with or without O2
define the following growth media classifications:
- complex
- defined
- enriched
- differential
- selective
- complex - numerous non-chemically defined nutrient sources (e.g. yeast)
- defined - all components are present in known amounts
- enriched - has components to help bacterial growth (i.e. blood)
- differential - allows differentiation of bacteria
- selective - allows growth of only certain bacteria
can a single growth medium have only one growth classification, or can it have multiple?
A single medium can have multiple characteristics (e.g. differential and selective).
fastidious bacteria:
define
- have specific growth/nutritional requirements.
- For this reason, a vast majority of the microbiota normal flora has not yet been cultured in the laboratory.
describe the selective and differential components of:
MacConkey’s agar
- selective - bile salts, crystal violet (accumulates in the cell to inhibit most Gram-positive bacteria), lactose
- differential - lactose as a C+E source and neutral red to detect acid production (red)
what does hemolysis allow for?
Fe-scavenging
(iron scavenging)
what test is used to determine if bacteria produce hemolysins?
blood agar plates (BAP)
what are the 3 types of hemolysis reactions, and define each?
- gamma-hemolysis (non hemolytic) = no detectable lysis
- alpha-hemolysis = partial lysis of RBCs surrounding the bacterial colony indicated by a green zone around the colony
- beta-hemolysis = complete lysis of RBCs surrounding the bacterial colony
can hemolysis be specific or non-specific?
both
e.g. can lyse mammalian cells from multiple species, or can be species specific
siderophores:
define and function
- small, high-affinity iron-chelating compounds secreted by bactera; amongst strongest soluble Fe3+ binding agents
- Fxn:
- serving to transport iron across cell membranes
- allow bacteria to scavenge iron from human proteins and from other bacteria
