hydrogenotrophic

Hydrogenotrophic refers to metabolism or organisms that derive energy by oxidizing molecular hydrogen (H2) and often obtain carbon from carbon dioxide (CO2). In hydrogenotrophy, H2 serves as the electron donor, while the electron acceptor varies by organism and environment. Many hydrogenotrophs are chemolithoautotrophs that fix CO2 into biomass, but some can also grow on organic carbon while using H2 to balance redox reactions.

Hydrogenotrophs include aerobic hydrogen-oxidizing bacteria that transfer electrons from H2 to oxygen, producing water, as well as anaerobic groups such as methanogenic archaea that reduce CO2 with H2 to methane, and sulfate- or nitrate-reducing bacteria that use H2 to reduce sulfate or nitrate. Notable examples are hydrogenotrophic methanogens (for instance, Methanobacteriales) and hydrogenotrophic sulfate-reducing bacteria (Desulfovibrio spp. and related taxa).

Ecological significance of hydrogenotrophy is broad. These organisms are common in oxygen-poor environments such as marine and freshwater sediments, wetlands, and hydrothermal vents, where they drive key steps in carbon and sulfur cycles and can support primary production in light-limited ecosystems. In host systems like ruminant guts, hydrogenotrophy contributes to fermentation-linked energy flows and gaseous byproducts.

Biochemical and genetic aspects include the use of specialized hydrogenases to catalyze H2 oxidation and, in autotrophic organisms, CO2 fixation via pathways such as the Wood-Ljungdahl pathway. Hydrogenotrophy thus represents a major strategy for microbial energy conservation and biogeochemical coupling in diverse environments.