The anaerobic chytridiomycete fungus Piromyces sp. E2 produces ethanol via pyruvate:formate lyase and an alcohol dehydrogenase E

Brigitte Boxma, Frank Voncken, Sander Jannink, Theo Van Alen, Anna Akhmanova, Susanne W.H. Van Weelden, Jaap J. Van Hellemond, Guenola Ricard, Martijn Huynen, Aloysius G.M. Tielens, Johannes H.P. Hackstein*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

70 Citations (Scopus)

Abstract

Anaerobic chytridiomycete fungi possess hydrogenosomes, which generate hydrogen and ATP, but also acetate and formate as end-products of a prokaryotic-type mixed-acid fermentation. Notably, the anaerobic chytrids Piromyces and Neocallimastix use pyruvate:formate lyase (PFL) for the catabolism of pyruvate, which is in marked contrast to the hydrogenosomal metabolism of the anaerobic parabasalian flagellates Trichomonas vaginalis and Tritrichomonas foetus, because these organisms decarboxylate pyruvate with the aid of pyruvate:ferredoxin oxidoreductase (PFO). Here, we show that the chytrids Piromyces sp. E2 and Neocallimastix sp. L2 also possess an alcohol dehydrogenase E (ADHE) that makes them unique among hydrogenosome-bearing anaerobes. We demonstrate that Piromyces sp. E2 routes the final steps of its carbohydrate catabolism via PFL and ADHE: in axenic culture under standard conditions and in the presence of 0.3% fructose, 35% of the carbohydrates were degraded in the cytosol to the end-products ethanol, formate, lactate and succinate, whereas 65% were degraded via the hydrogenosomes to acetate and formate. These observations require a refinement of the previously published metabolic schemes. In particular, the importance of the hydrogenase in this type of hydrogenosome has to be revisited.

Original languageEnglish
Pages (from-to)1389-1399
Number of pages11
JournalMolecular Microbiology
Volume51
Issue number5
DOIs
Publication statusPublished - Mar 2004
Externally publishedYes

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