chemolitotrophic

Chemolithotrophy, also known as lithoautotrophy, is a form of metabolism in which organisms derive energy from the oxidation of inorganic compounds and fix carbon dioxide as a carbon source. Organisms capable of this metabolism are called chemolithotrophs or lithoautotrophs. They typically live in environments where organic carbon is scarce or where inorganic electron donors are abundant.

Energy and carbon sources in chemolithotrophy come from inorganic substrates. Potential electron donors include hydrogen (H2), reduced sulfur compounds (such as hydrogen sulfide H2S, elemental sulfur S0, or thiosulfate), ammonia (NH3), nitrite (NO2-), ferrous iron (Fe2+), and other reduced metals. Electron acceptors vary: oxygen in aerobic chemolithotrophs, or alternative acceptors such as nitrate, ferric iron, or sulfate under anaerobic conditions. Most chemolithotrophs are autotrophs that fix CO2 through pathways such as the Calvin cycle, reverse Krebs (reverse TCA) cycle, or the Wood–Ljungdahl pathway.

Ecologically, chemolithotrophs are important primary producers in many ecosystems, including soils, caves, hot springs, deep-sea hydrothermal vents, and acidic mine drainage. They drive biogeochemical cycles of nitrogen, sulfur, and iron, and can influence mineral weathering and bioleaching. Some chemolithotrophs have applications in bioremediation and bioenergy.

Notable examples include ammonia-oxidizing bacteria such as Nitrosomonas, nitrite-oxidizing bacteria such as Nitrobacter, sulfur-oxidizing bacteria like Thiobacillus and Acidithiobacillus, and iron-oxidizing members such as Leptospirillum and Ferrooxidans. Hydrogen-oxidizing bacteria and certain archaea (for example, Sulfolobus) also contribute to chemolithotrophic metabolism.

Chemolithotrophy is distinct from chemoorganotrophy, which uses organic electron donors, and from phototrophy, which uses light as an energy source.