Fundamentals of Microbiology

2.4.4 Chemoautotrophs

Chemoautotrophs use the electrons from reduced inorganic compounds as a source of energy, and they use CO₂ as their principal source of carbon. Inorganic sources of energy for these organisms include hydrogen sulfide (H₂S) for Beggiatoa; elemental sulfur (S) for Thiobacillus thiooxidans; ammonia (NH₃) for Nitrosomonas; nitrite ions (NO^-₂) for Nitrobacter; hydrogen gas (H2) for Hydrogenomonas; and ferrous iron (Fe²⁺) for Thiobacillus ferrooxidans. The energy derived from the oxidation of these inorganic compounds is eventually stored in ATP, which is produced by oxidative phosphorylation.