Source organisms A non-exhaustive list of organisms containing hydrogenosomes includes: parabasalid flagellates (e.g. Trichomonas vaginalis, Tritrichomonas foetus, Histomonas meleagridis) preaxostylid flagellates (e.g. Trimastix pyriformis) heterolobosean amoeboflagellates (e.g. Psalteriomonas lanterna) anaerobic ciliates (e.g. Nyctotherus ovalis, Metopus palaeformis, Trimyema compressum, Caenomorpha uniserialis, Dasytricha ruminantium) anaerobic chytridiomycete fungi (e.g. Neocallimastix spp., Piromyces spp.) The vast variety of source organisms can be accredited to the theorized convergent evolution of hydrogenosomes from mitochondria to fit an anaerobic environment. In 2010, scientists have also reported their discovery of the first known anaerobic metazoans with hydrogenosome-like organelles. Three multicellular species of Loricifera — Spinoloricus nov. sp., Rugiloricus nov. sp. and Pliciloricus nov. sp. — have been found deep in Mediterranean sediments, and use hydrogenosomes in their anaerobic metabolism cycle. ATP Synthesis 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. See also Mitochondria Mitosome Plastid References Organelles