chemolithotrophic

Chemolithotrophy is a metabolic strategy in which organisms obtain energy by oxidizing inorganic compounds and use carbon dioxide or other inorganic carbon sources for growth. Chemolithotrophs may be autotrophic, fixing CO2, or may use organic carbon when available, but they consistently derive electrons from inorganic substrates rather than from organic matter.

Energy is obtained through redox reactions in which inorganic electron donors such as hydrogen (H2), reduced sulfur compounds (e.g., sulfide, thiosulfate), ammonia (NH3), nitrite (NO2−), or ferrous iron (Fe2+) donate electrons to an electron transport chain. The terminal electron acceptor may be oxygen in aerobic chemolithotrophy, or inorganic compounds such as nitrate, ferric iron, or sulfate in anaerobic chemolithotrophy.

Most chemolithotrophs are autotrophs and fix CO2 using pathways like the Calvin cycle, the reverse tricarboxylic acid cycle, or hydroxypropionate cycles.

Ecology: They are common in soils, freshwater, and marine environments, and dominate primary production in dark or inorganic environments such as deep-sea hydrothermal vents, sulfur springs, and oxic–anoxic interfaces. Examples include Nitrosomonas (ammonia-oxidizing), Nitrobacter (nitrite-oxidizing), Thiomicrospira and Thiobacillus (sulfur-oxidizing), Acidithiobacillus ferrooxidans (iron-oxidizing), and hydrogen-oxidizing bacteria such as Hydrogenobacter.

History: The concept of chemolithotrophy was developed by Sergei Winogradsky in the 1880s as part of his studies on lithotrophic bacteria.