The first genetic evidence of hydrogenosomes—organelles found in some ciliates, trichomonads, and fungi that generate hydrogen and adenosine triphosphate (ATP)—that evolved from mitochondria is reported by Dutch and German researchers in
"Our findings prove the existence of missing links between mitochondria and hydrogenosomes," coauthor Johannes Hackstein of Radboud University Nijmegen in the Netherlands told
Hydrogenosomes resemble mitochondria morphologically, but generally lack a genome, hampering clarification of their origin. Considerable debate exists over whether hydrogenosomes evolved from aerobically functioning mitochondria that acquired an anaerobic metabolism or from endosymbionts capable of both aerobic and anaerobic function that mitochondria also descended from.
In 1998, Hackstein and colleagues found preliminary evidence that hydrogenosomes of the anaerobic ciliate