Bacterial Nutrition, Metabolism, & Growth Flashcards
Heterotrophic metabolism
The sources of energy & carbon are organic carbon sources (carbohydrates, protein, lipid).
–> most pathogenic bacteria are heterotrophic.
2 forms: respiration & fermentation
Autotrophic metabolism
Fixes CO2
- cellular energy is obtained from oxidation/reduction of inorganic ions (chemoautotroph)
- or harvesting light energy (photoautotroph)
Halophile
Salt loving bacteria
Ex:
Vibrio cholera
Low or elevated levels of ______ can serve as triggers fm for pathogens.
Iron
Low levels of Fe induces Corynebacrerium diphtheriae to produce diphtheria toxin.
During an infection the human body sequesters Fe & excretes the excess to keep it away from bacteria.
Mesophiles
Growth occurs between 20-55 degrees C
Most grow best at body temp (35-36C)
Thermophiles
Obligate or facultative
Grow at temps greater than 55C
Psychrophiles & Cryophiles
Grow at temps <20C
Is refrigeration a acceptable method of maintaining or obtaining sterile conditions?
NO!!!!
How can Aerobes & facultative aerobes can grow in the presence of O2?
b/c produce enzymes which by detoxify superoxide radicals & hydrogen peroxide.
–> Superoxide dismutase (SOD) detoxifies O2
Obligate aerobes
Require the presence of atmospheric O2 for growth.
–> mycobacterium tuberculosis.
Microaerophilc organisms
Require the presence of some O2 but NOT at atmospheric levels (reduced O2)
E.g. Campylobacter
Facultative anaerobes
Can grow in the presence or absence of O2.
Many pathogens are facultative anaerobes!!
Ex: enteric bacteria
Aerotolerant anaerobes
Can survive in the presence of O2
Ex: lactobacillus
Obligate anaerobes
Killed by the presence of O2.
Ex: Clostridium, bacteroides, & others.
(Lack in the enzymes superoxide dismutase & catalase)
Respiration
An enzymatic process but it is a unique enzymatic process must occur in a membrane vesicle or sack.
Provides energy via proton motive force for ATP synthesis (prod) during the conversion (recycling) of NADH2 to NAD
Catalase
Detoxifies hydrogen peroxide (H2O2) produced by superoxide dismutase
Superoxide dismutase
Detoxifies O2 (superoxide anion)
Aerobic respiration
Oxidative phosphorylation
O2 is the terminal electron acceptor –> reduced by the electron transport system.
Common in pathogenic microorganisms & humans
Anaerobic respiration
Inorganic compounds (nitrite, sulfate, etc.) serve as terminal electron acceptors.
Any organism w/ the nitrate reductase pathway is able to grow in the absence of oxygen in the presence of nitrate, which is present in inflam processes.
Ex: pseudomonas aeruginosa
Fermentation
Results in the incomplete oxidation of a carbon substrate. Fermentation is less efficient process than respiration.
Fermentation consists of catabolic pathways where organic compounds serve as electron donor is an electronic accepters.
substrates are partially oxidized, generating end products which:
1. Are carbon compounds
2. Serve as the electron acceptor (accept e- & H+)
3. Are released from the cell.
Pyruvate–> ETOH+CO2
Dental carries
Caused by streptococcus mutans which produce lactic acid (via fermentation)
Acidification of skin & vagina:
By lactobacillus sp. which prod lactic acid
& Propionibacterium acnes which prod Propionic acid via fermentation
Abscesses are ________ & ________ d/t fermentative metabolism of bacteria in the abscess
Acidic & anaerobic
How are abscesses able to thrive?
Many antibiotics are not effective at low pHs. Acidic
Low pH kills surrounding viable human cells including phagocytes.
In fermentation, organisms do not use NAD or NADP as e- and H+ carrier, but rather _________ is used
Ferredoxin
What is required to recycle reduced ferredoxin to the oxidized form?
Hydrogen lyase
Clostridium perfringens
Can cause gas gangrene (myonecrosis)
–> produces hydrogen gas which is insoluble in tissues. It tracks along Fascial planes separating muscle tissues (thus gains bacteria access to fresh tissue), collapses blood vessels, impedes perfusion, all of which help to create anaerobic conditions.
Dextrans
Synthesized from sucrose by Streptococcus mutans.
In dental plaque
Can be H2O soluble –> noncaryogenic plaque= fructosyltransferase.
Cariogenic –> glucosyltransferase
Proteus spp. Causes what type of infection?
UTIs
Produces ammonia –> increases urine pH
–> more alkaline–> calculi (kidney stones)
Helicobacter pylori
Can cause stomach ulcers or CA.
Produces ammonia –> raises the microenvironment pH
Transpeptidase or penicillin binding protein play a role in synthesis of ____________
Peptidoglycan
Selected for by many antibiotics.
