An anaerobic mitochondrion that produces hydrogen

Change in the air Hydrogenosomes are simple organelles found in anaerobic protists and fungi. They are double-membraned and produce ATP and hydrogen, hence suggestions that they are anaerobic derivatives of mitochondria. An alternative view suggests that mitochondria and hydrogenosomes arose from a common ancestor, a facultatively anaerobic bacterium. The discovery of a novel hydrogenosome in Nyctotherus ovalis, a ciliate that lives in the gut of cockroaches, further complicates this debate. It is unique among known hydrogenosomes because, just like a mitochondrion, it retains its own genome. This ‘missing link’ between hydrogenosomes and mitochondria also has remnants of an electron transport chain characteristic of an aerobic lifestyle.