chemoautotrofy

Chemoautotrophy is a form of autotrophy in which organisms obtain energy by oxidizing inorganic molecules and use carbon dioxide as their primary carbon source. Chemoautotrophs derive energy from chemical reactions involving inorganic substrates rather than sunlight, and they synthesize organic compounds from CO2 to support growth.

Common inorganic energy sources include ammonia or ammonium, nitrite, sulfide and elemental sulfur, ferrous iron, and molecular hydrogen. Depending on the organism, carbon fixation may proceed via pathways such as the Calvin cycle, the reverse tricarboxylic acid cycle, or other carbon-conserving routes. This allows chemoautotrophs to inhabit environments where light is scarce or absent, by tapping energy from redox reactions of inorganic molecules.

Chemoautotrophs encompass a range of bacteria and archaea. Examples of bacteria include ammonia-oxidizing forms such as Nitrosomonas, nitrite-oxidizing bacteria like Nitrobacter, and sulfur-oxidizing genera such as Thiomicrospira and Thiobacillus; iron-oxidizing bacteria also contribute to chemoautotrophic metabolism. Archaea include several ammonia-oxidizing lineages and other groups that perform inorganic energy workflows. These organisms often live in nutrient-poor or extreme environments, including deep-sea hydrothermal vents, cold seeps, sulfur springs, iron-rich soils and mines, as well as in symbiotic relationships with host organisms.

Chemoautotrophy plays a key role in global biogeochemical cycles, supporting primary production in darkness and contributing to nutrient cycling in many ecosystems. It has potential applications in bioleaching, biomining, bioremediation, and industrial microbiology.