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Table 1 Metabolic diversity and redox reactions

From: The Never-Ending Story-The Origin and Diversification of Life

Conditions e- donor e- acceptor Examplesa
Anaerobic H2 CO Acetogenesis - CO + H2 → CH3COOH + H2O
  H2 CO2 Acetogenesis - CO2 + H2 → CH3COOH + H2O
  H2 CO2 Methanogenesis - CO2 + H2 → CH4 + H2O
  H2 CO2 Anoxygenic photosynthesis - CO2 + H2 + hv → CH2O + H2O
  H2 SO42- Sulfate reduction - SO 4 2 - + H + + H 2 H S - + H 2 O
  H2 S Sulphur reduction - S + H2 → H2S
  H2 NO3- Denitrification - H 2 + NO 3 - N 2 + H 2 O
  H2S CO2 Anoxygenic photosynthesis - C O 2 + H 2 S + h v C H 2 O + SO 4 2 -
  H2S NO3- Nitrate reduction - NO 3 - + H 2 S N 2 + SO 4 -
  Fe2+ CO2 Anoxygenic photosynthesis - CO2 + FeO + hv → CH2O + Fe2O3
  As3+ CO2 Anoxygenic photosynthesis - As3+ + CO2 + hv → CH2O + As5+ + H2O
  NH4+ (and NO2-) NO2 (and CO2) Annamox NH 4 + + NO 2 + HCO 3 + H + N 2 + NO 3 + H 2 O + CH 2 O 1 ) + NH 4 + + NO 2 N 2 2 ) NO 2 + CO 2 CH 2 O + H 2 O
  CH4 SO42- Methane oxidation - C H 4 + SO 4 2 - C O 2 + H 2 S + H 2 O
  CH2O NO3- Denitrification - C H 2 O + NO 3 - + H + N 2 + C O 2 + H 2 O
  CH3CO2- Fe3+ Iron reduction - F e 3 + + C H 3 CO 2 - + H 2 O HCO 3 - + F e 2 + + H +
  C6H12O6 NAD+ Fermentation - C6H12O6 + NAD+ → C2H6O + CO2 + NADH + H2
Aerobic H2O CO2 Oxygenic photosynthesis - CO2 + H2O + hv → CH2O + O2 + H2O
  (CH2O) O2 Respiration - CH2O + O2 → CO2 + H2O
  CH4 O2 Methane oxidation - C H 4 + O 2 HCO 3 - + H + + H 2 O
  Mn2+ O2 Manganese oxidation - Mn2+ + O2 + H2O → MnO2 + H+
  H2 O2 Hydrogen oxidation - H2 + O2 → H2O
  HS- O2 Sulfide oxidation - H S - + O 2 SO 4 2 - + H +
  NH4+ O2 Nitrification - NH 4 + + O 2 NO 2 - + H + + H 2 O
  NO2-   NO 2 - + O 2 NO 3 -
  Fe2+ O2 Iron oxidation - Fe2+ + H+ + O2 → Fe3+ + H2O
  1. CH2O refers to an idealized reduced organic carbon (including pyruvate, acetate, formate, fumurate, methanol, etc.)
  2. hv electromagnetic radiation
  3. a Equations are unbalanced, and some of the chemoautotrophic pathways do not illustrate carbon reduction, as many of these organisms are mixotrophs, employing both autotrophic and heterotrophic mechanisms based on context