Chemosynthesis

Chemosynthesis is a metabolic pathway used by some bacteria to synthesize new organic compounds such as carbohydrates by using energy derived from the oxidation of inorganic molecules—hydrogen sulfide (H₂S) or ammonia (NH₃). Chemosynthesis can occur in environments such as the deep ocean around hydrothermal vents , where sunlight does not penetrate, but where chemicals like hydrogen sulfide are available. Chemosynthesis is also a critical part of the nitrogen cycle , where bacteria that live in the soil , or in special plant structures called heterocysts, utilize ammonia for energy and produce nitrates and nitrites which can subsequently be used as nutrients for plants. Some bacteria can also utilize hydrogen gas (H₂) and carbon dioxide (CO₂) in a chemosynthetic pathway that results in the production of new organic compounds and methane (CH₄).

[Marie H. Bundy ]

che·mo·syn·the·sis / ˌkēmōˈsin[unvoicedth]əsəs; ˌkemō-/ • n. Biol. the synthesis of organic compounds by bacteria or other living organisms using energy derived from reactions involving inorganic chemicals, typically in the absence of sunlight. Compare with photosynthesis.DERIVATIVES: che·mo·syn·thet·ic / -sinˈ[unvoicedth]etik/ adj.

chemosynthesis The pathway by which bacteria in hydrothermal vent communities synthesize complex organic molecules from hydrogen sulphide gas and dissolved carbon dioxide: 4H₂S + CO₂ + O₂ → CH₂O + 4S + 3H₂O.

chemosynthesis A type of autotrophic nutrition in which organisms (called chemoautotrophs) synthesize organic materials using energy derived from the oxidation of inorganic chemicals, rather than from sunlight. Most chemoautotrophs are bacteria, including Nitrosomonas, which oxidizes ammonium to nitrite; and Thiobacillus, which oxidizes sulphur to sulphate.