Bacterial Metabolism Flashcards
Metabolism:
anabolism + catabolism
What types of energy sources cells can use ?
- Chemical: chemotrophs
2. Light: Phototrophs
Photosynthesis :
Light energy is absorbed by pigments (e.g chlorophyll) and converted into chemical
energy (ATP) thanks to electron transport chains embedded in the cell membrane
(plasma membrane, thylakoid membrane) of photosynthetic bacteria
Anoxygenic photosynthesis
(green and purple bacteria)
Aerobic respiration:
Electron transport chain in the plasma membrane
Aerobic respiration: final electron acceptor: O2
O2
: High redox potential. The more energy-efficient respiration type
(highest ATP production, ~30 molecules)
Electron donors (carbohydrates, proteins, a.a, etc)
Anaerobic respiration:
Electron transport chain in the plasma membrane
Anaerobic respiration: final electron acceptor: Different from O2
The final electron acceptor have lower reduction potential than oxygen.
Less energy is formed than in aerobic respiration.
fermentation :
No use of electron transport chains
Final electron acceptor: organic compound (e.g pyruvate)
Electron donor : organic compound
Very low efficiency
Different types: ethanol, lactic acid fermentation, etc…
obligate aerobes : O2 required
(Pseudomonas)
microaerophiles : O2 required in low concentration
(Campylobacter)
- facultative anaerobes : can grow without O2 but greater growth in presence of O2
(E. coli)
aerotolerant anaerobes : don’t need O2 but tolerate O2
(Enterococcus)
obligate anaerobes** : cannot tolerate O
Clostridium)
Chemo organotrophic metabolisms
Prokaryotes can use of a wide range of natural organic molecules as electron
donors. e.g in aerobic and anaerobic respiration: carbohydrates (pentoses, hexoses,
polysaccharides) , proteins, amino acids, lipids, hydrocarbon…
Chemo lithotrophic metabolisms
Aerobic and anaerobic respirations.
e.g anaerobic respiration:
- Acetogens: e.g acetogenic bacteria producing acetate
- Methanogens: e.g methanogenic Archaea reducing CO2 and producing
methane
