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

Fungi form a very diverse group of eukaryotes. The majority of investigated fungi contain mitochondria and are capable of oxidative phosphorylation. On the other hand, anaerobically functioning chytridiomycete fungi, 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 produce hydrogen and ATP by substrate-level phosphorylation. However, in contrast to the hydrogenosomes of trichomonads and anaerobic ciliates, the hydrogenosomes of the anaerobic chytrids Neocallimastix and Piromyces lack pyruvate dehydrogenase (PDH) and pyruvate-ferrodoxin oxidoreductase (PFO) and instead contain pyruvate-formate lyase (PFL). The function in carbohydrate metabolism of these hydrogenosomes of anaerobic chytridiomycete fungi and their evolutionary relation to fungal mitochondria is discussed. [ABSTRACT FROM AUTHOR]