Carbon fixation pathways Also known as Organisms Key CO2 fixating enzymes Key CO2fixating reaction Calvin-Benson-Bassham cycle (CBB) Reductive pentose phosphate cycle Plants, algae, cyanobacteria, proteobacteria, mycobacteria RuBisCO Ribulose-1,5-bisphosphate + CO2 + H2O → 2´ 3-Phosphoglycerate Reductive tricarbocylic acid cycle (rTCA) Reductive citric acid cycle/Reverse Krebs cycle/Arnon-Buchanon cycle Proteobacteria, green sulfur bacteria, aquaficae bacteria Phosphoenolpyruvate carboxylase2-Oxogluterate synthase Isocitrate dehydrogenasePyruvate synthase Phosphoenolpyruvate + HCO3- → Oxaloacetate + PiSuccinyl-CoA + CO2 + Fdred2- + 2H+ → 2-Oxoglutarate + CoA + Fdox2-Oxogluterate + CO2 + NAD(P)H + H+ → Isocitrate + NAD(P)+Acetyl-CoA + CO2 + Fdred2- + 2H+ → Pyruvate + CoA + Fdox Wood-Ljungdahl pathway (W-L) Reductive acetyl-CoA pathway Euryarchaeota, proteobacteria, plantomycetes, spirochaetes Formate dehydrogenaseCO dehydrogenase/Acetyl-CoA synthase Formylmethanofurandehydrogenase* CO2 + NAD(P)H + H+ → Formate + NAD(P)+ CO2 + 2H+ + 2e- → CO + H2O CO + CH3-CFeSP + HSCoA → CH3-CO-SCoA + CFeSP + H+Methanofuran + CO2 + 2H+ + Fdred2- → Formylmethanofuran + H2O + Fdox 3-Hydroxypropionate-4-hydroxybutyrate cycle (3HP-4HB)   Aerobic crenarcheota Acetyl-CoA/Propionyl-CoA carboxylaseAcetyl-CoA/Propionyl-CoA carboxylase Acetyl-CoA + ATP + HCO3- → Malonyl-CoA + ADP + Pi Propionyl-CoA + ATP + HCO3- → (S)-Methylmalonyl-CoA + ADP + Pi Dicarboxylate-4-hydroxybutyrate cycle (DC-4HB)   Anaerobic crenarcheota Pyruvate synthasePhosphoenolpyruvate carboxylase Acetyl-CoA + CO2 + Fdred2- → Pyruvate + Fdox Phosphoenolpyruvate + HCO3- → Oxaloacetate + Pi 3-Hydroxypropionate bi-cycle (3-HP) Fuchs-Holo cycle Green non-sulfur bacteria Acetyl-CoA carboxylasePropionyl-CoA carboxylase Acetyl-CoA + ATP + HCO3- → Malonyl-CoA + ADP + Pi Propionyl-CoA + ATP + HCO3- → (S)-Methylmalonyl-CoA + ADP + Pi *Found in methanogenic Archaebacteria

Table 1: Reported carbon fixation pathways.