Hydrogenosomes: Origin

Recent hydrogenosomes have apparently different origins and have evolved several times at different places. As is shown in molecular biological analysis and in phylogenetic reconstructions of rRNA data, they represent strongly reduced anaerobic stages like mitochondria (without inner invaginations). In general DNA is absent in hydrogenosomes and their essential proteins are encoded inside the nucleus of the cell. As mitochondria hydrogenosomes have the same evolutionary origin since that in both cases, a free-living proteobacterium was engulfed by a cell and stayed there as endosymbiont. They possess therefore like recent mitochondria two limiting membranes consisting of phospho- and glycolipids. In contrast to mitochondria, hydrogenosomes obtain their energy by phosphorylation by the help of substrate chains, while mitochondria use an electron transportation chain. As well as in contrast to mitochondria, most hydrogenosomes have no own genome, and thus all their proteins are encoded...