Chemolithotrophy

Abstract

Abstract Many prokaryotes, Bacteria as well as Archaea , obtain their energy from the oxidation of reduced inorganic compounds such as hydrogen, ammonia, nitrite, sulfide, elemental sulfur, hydrogen and Fe(II) ions. These organisms can derive all their cellular carbon from carbon dioxide, and they are thus able to grow without any organic compounds and without light. Such microorganisms are called chemolithotrophs or chemoautotrophs. Chemolithotrophic life is possible in the presence as well as in the absence of molecular oxygen. Processes mediated by chemolithotrophic prokaryotes include nitrification (the formation of nitrate from ammonia), production of sulfuric acid from sulfide and elemental sulfur, and the formation of methane from hydrogen and carbon dioxide. Some ecosystems, for example those that develop around deep‐sea hot vents, are entirely driven by carbon fixed by chemolithotrophic microorganisms. Key concepts Certain groups of prokaryotes obtain their energy from the oxidation of reduced inorganic compounds such as sulfide, ammonia and hydrogen, and use carbon dioxide as carbon source. These organisms are called chemolithotrophs or chemoautotrophs. Chemolithotrophy is widespread in the two domains of prokaryotes: the Bacteria and the Archaea . Many chemolithotrophs use molecular oxygen as electron acceptor, but chemolithotrophy is also possible in the absence of oxygen. Nitrate, sulfate, elemental sulfur or carbon dioxide serves as electron acceptors for certain groups of chemolithotrophs. Nitrification, or the oxidation of ammonia via nitrite to nitrate by chemolithotrophic bacteria, is a key process in the global nitrogen cycle. Two types of anaerobic chemolithotrophs oxidize hydrogen with carbon dioxide as electron acceptor: methanogens and homoacetogens, producing methane and acetate, respectively. Chemolithotrophs participate in the biogeochemical cycles of certain metals (iron, manganese) and metalloids (arsenic). In some environments such as deep‐sea hydrothermal vents and certain underground caves, chemolithotrophic primary production driven by the oxidation of hydrogen sulfide provides the basis for the functioning of the ecosystem.