Hydrogenosome

A hydrogenosome is a membrane-enclosed organelle of some anaerobic ciliates, trichomonads and fungi. The hydrogenosomes of trichomonads (the most studied of the hydrogenosome-containing microorganisms) produce molecular hydrogen, acetate, carbon dioxide and ATP by the combined actions of pyruvate:ferredoxin oxido-reductase, hydrogenase, acetate:succinate CoA transferase and succinate thiokinase. Superoxide dismutase, malate dehydrogenase (decarboxylating), ferredoxin, adenylate kinase and NADH:ferredoxin oxido-reductase are also localized in the hydrogenosome. This organelle is thought to have evolved from anaerobic bacteria or archaea, though in the case of trichomonad hydrogenosomes the question remains open.

In 2010, scientists reported their discovery of the first known anaerobic metazoans with hydrogenosome-like organelles.