Nitrite-driven anaerobic methane oxidation by oxygenic bacteria

Katharina F. Ettwig (1) , Margaret K. Butler (1) , Denis Le Paslier (2, 3) , Eric Pelletier (2, 3) , Sophie Mangenot (2) , Marcel M. M. Kuypers (4) , Frank Schreiber (4) , Bas E. Dutilh (5) , Johannes Zedelius (4) , Dirk de Beer (4) , Jolein Gloerich (6) , Hans J. C. T. Wessels (6) , Theo van Alen (1) , Francisca Luesken (1) , Ming L. Wu (1) , Katinka T. van de Pas-Schoonen (1) , Huub J. M. Op den Camp (1) , Eva M. Janssen-Megens (5) , Kees-Jan Francoijs (5) , Henk Stunnenberg (5) , Jean Weissenbach (2, 3) , Mike S. M. Jetten (1, 7) , Marc Strous (8)

1 IWWR, Department of Microbiology
2 GENOSCOPE - Genoscope - Centre national de séquençage [Evry]
3 SEG - Structure et évolution des génomes - UMR 8030
4 Max Planck Institute for Marine Microbiology
5 Department of Molecular Biology [Nijmegen]
6 Department of Laboratory Medicine, Laboratory of Genetic, Endocrine and Metabolic Diseases
7 Department of Aquatic Ecology & Environmental Biology
8 Department of Microbiology

Only three biological pathways are known to produce oxygen: photosynthesis, chlorate respiration and the detoxification of reactive oxygen species. Here we present evidence for a fourth pathway, possibly of considerable geochemical and evolutionary importance. The pathway was discovered after metagenomic sequencing of an enrichment culture that couples anaerobic oxidation of methane with the reduction of nitrite to dinitrogen. The complete genome of the dominant bacterium, named 'Candidatus Methylomirabilis oxyfera', was assembled. This apparently anaerobic, denitrifying bacterium encoded, transcribed and expressed the well-established aerobic pathway for methane oxidation, whereas it lacked known genes for dinitrogen production. Subsequent isotopic labelling indicated that 'M. oxyfera' bypassed the denitrification intermediate nitrous oxide by the conversion of two nitric oxide molecules to dinitrogen and oxygen, which was used to oxidize methane. These results extend our understanding of hydrocarbon degradation under anoxic conditions and explain the biochemical mechanism of a poorly understood freshwater methane sink. Because nitrogen oxides were already present on early Earth, our finding opens up the possibility that oxygen was available to microbial metabolism before the evolution of oxygenic photosynthesis

Domaines: Microbiologie et Parasitologie

Katharina F. Ettwig, Margaret K. Butler, Denis Le Paslier, Eric Pelletier, Sophie Mangenot, et al.. Nitrite-driven anaerobic methane oxidation by oxygenic bacteria. Nature, 2010, 464 (7288), pp.543-548. ⟨10.1038/nature08883⟩. ⟨cea-00907649⟩