Hydrogenosome

Hydrogenosomes (hydrogen v. English, " hydrogen " ) are organelles that in some ciliates, trichomonads and potty fungi ( Chytridiomycota ) occur instead of mitochondria and allow survival under anaerobic conditions. The approximately one micrometre organelles were described in 1973 for the first time. All hydrogenosomes probably came from one mitochondrion. It was lost in almost all cases the genome. Only in the hydrogenosomes of the ciliate Nyctotherus ovalis is still a small genome available. Accordingly, there is an intermediate form ( Missing Link ) in the evolution of the mitochondrion to hydrogenosome represents the two organelles show various similarities: They are surrounded by two membranes that produce adenosine triphosphate ( ATP), occur in many copies and divide without synchronization during the throughout the cell cycle.

In contrast to the mitochondria to hydrogenosomes lack a genome own (except for N. ovalis ), respiratory chain cytochromes, FoF1 -ATPase, citric acid cycle, oxidative phosphorylation, and cardiolipin. While mitochondria operate exclusively an aerobic respiration, fermentation under anaerobic allow hydrogenosomes and aerobic conditions ( Fig. 1). A first substrate for the substrate chain, seen from the ATP of pyruvate, the final product of glycolysis takes place in the cytosol is. Phosphorylation of adenosine diphosphate ( ADP) into ATP catalyzed by the succinyl-CoA synthetase. The byproducts of ATP synthesis are under anaerobic conditions acetate and hydrogen, which is eponymous for the hydrogenosomes. Under aerobic conditions, is probably formed hydrogen peroxide instead of hydrogen.