Hydrogenosomes of Anaerobic Chytrids: An Alternative Way to Adapt to Anaerobic Environments

Abstract

Fungi form a very diverse group of eukaryotes. The majority of investigated fungi contain mitochondriaand are capable of oxidative phosphorylation. On the other hand, anaerobically functioning chytridiomycetefungi, found as symbionts in the gastrointestinal tract of many herbivorous mammals, contain hydrogenosomes.These organelles are found in multiple classes of protozoa and catabolize glycolytic end products and producehydrogen and ATP by substrate-level phosphorylation. However, in contrast to the hydrogenosomes of trichomonadsand anaerobic ciliates, the hydrogenosomes of the anaerobic chytrids Neocallimastixand Piromyces lack pyruvate dehydrogenase (PDH) and pyruvate-ferrodoxinoxidoreductase (PFO) and instead contain pyruvate-formate lyase (PFL). The function in carbohydrate metabolismof these hydrogenosomes of anaerobic chytridiomycete fungi and their evolutionary relation to fungal mitochondriais discussed.