Lithotrophie

Lithotrophie, or lithotrophy, is a metabolic strategy in which cells obtain electrons from reduced inorganic compounds to drive their energy metabolism. Lithotrophs derive energy from the oxidation of inorganic electron donors such as molecular hydrogen (H2), reduced sulfur species (H2S, S0, thiosulfate), ferrous iron (Fe2+), and reduced nitrogen compounds (NH3/NH4+, NO2−). In contrast to organotrophy, where organic compounds serve as electron donors, lithotrophy relies on inorganic substrates.

Most lithotrophs are chemoautotrophs: they fix carbon dioxide or bicarbonate as their primary carbon source, using energy generated from inorganic oxidation. Some lithotrophs can assimilate organic carbon and are described as lithoheterotrophs, illustrating metabolic flexibility in natural environments. Lithotrophs can be aerobic or anaerobic, and some participate in energy-conserving processes such as lithoautotrophy coupled to oxygen, nitrate, or other electron acceptors.

Ecologically, lithotrophs play key roles in global biogeochemical cycles, notably the nitrogen, sulfur, and iron cycles. They are found in diverse habitats, including soils, sediments, freshwater and marine systems, hot springs, hydrothermal vents, acidic mine drainages, and permafrost environments. Taxonomically, lithotrophs span bacteria and archaea, from ammonia-oxidizing bacteria like Nitrosomonas to sulfur-oxidizing Acidithiobacillus and iron-oxidizers such as Acidithiobacillus ferrooxidans.

Applications include bioleaching, bioremediation, and niche ecological studies. Lithotrophy is distinct from phototrophy (energy from light) and from organotrophy (electrons from organic compounds), representing a major mode of microbial energy conservation.