acetogens

Acetogens are microorganisms that produce acetate as the main end product of anaerobic metabolism. They are primarily bacteria, although some archaea also perform acetogenesis. Acetogenesis occurs via the reductive acetyl-CoA pathway, commonly known as the Wood-Ljungdahl pathway, which enables growth on carbon dioxide and various electron donors.

In the Wood-Ljungdahl pathway, CO2 is reduced and incorporated into a methyl group and, together with a carbon monoxide-equivalent, condensed with coenzyme A to form acetyl-CoA. This acetyl-CoA is then converted to acetate, a reaction that yields ATP and supports energy conservation. Many acetogens use hydrogen or formate as electron donors, and some can assimilate organic substrates as well.

Acetogens occupy a wide range of anaerobic habitats. They are found in freshwater and marine sediments, wetlands, soil, and the guts of termites and ruminant animals, as well as in industrial and laboratory anaerobic reactors designed for waste treatment and biogas production. Their activity links carbon dioxide to acetate and thus participates in the global carbon cycle, often in syntrophic associations with other microbes, including hydrogenotrophic methanogens.

Ecological and biotechnological significance: acetogens contribute to carbon cycling under anaerobic conditions and are explored for renewable acetate production and carbon capture strategies. In engineered systems, they can partner with methanogens or other microbes to improve waste degradation and energy recovery.

Notable members include Acetobacterium woodii and Moorella thermoacetica, both classic models for studying acetogenic metabolism.