Raghoebarsing Ashna A, Pol Arjan, van de Pas-Schoonen Katinka T, Smolders Alfons J P, Ettwig Katharina F, Rijpstra W Irene C, Schouten Stefan, Damsté Jaap S Sinninghe, Op den Camp Huub J M, Jetten Mike S M, Strous Marc
Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands.
Nature. 2006 Apr 13;440(7086):918-21. doi: 10.1038/nature04617.
Modern agriculture has accelerated biological methane and nitrogen cycling on a global scale. Freshwater sediments often receive increased downward fluxes of nitrate from agricultural runoff and upward fluxes of methane generated by anaerobic decomposition. In theory, prokaryotes should be capable of using nitrate to oxidize methane anaerobically, but such organisms have neither been observed in nature nor isolated in the laboratory. Microbial oxidation of methane is thus believed to proceed only with oxygen or sulphate. Here we show that the direct, anaerobic oxidation of methane coupled to denitrification of nitrate is possible. A microbial consortium, enriched from anoxic sediments, oxidized methane to carbon dioxide coupled to denitrification in the complete absence of oxygen. This consortium consisted of two microorganisms, a bacterium representing a phylum without any cultured species and an archaeon distantly related to marine methanotrophic Archaea. The detection of relatives of these prokaryotes in different freshwater ecosystems worldwide indicates that the reaction presented here may make a substantial contribution to biological methane and nitrogen cycles.
现代农业在全球范围内加速了生物甲烷和氮的循环。淡水沉积物常常会接收到来自农业径流中增加的硝酸盐向下通量以及厌氧分解产生的甲烷向上通量。理论上，原核生物应该能够利用硝酸盐进行甲烷的厌氧氧化，但这类生物在自然界中尚未被观察到，在实验室中也未被分离出来。因此，人们认为甲烷的微生物氧化仅在有氧气或硫酸盐的情况下进行。在此，我们表明甲烷与硝酸盐反硝化作用耦合的直接厌氧氧化是可能的。从缺氧沉积物中富集得到的一个微生物群落，在完全无氧的情况下将甲烷氧化为二氧化碳并与反硝化作用耦合。这个群落由两种微生物组成，一种细菌代表一个尚无任何培养物种的门，另一种古菌与海洋甲烷营养型古菌有较远的亲缘关系。在全球不同淡水生态系统中对这些原核生物亲缘种的检测表明，此处所呈现的反应可能对生物甲烷和氮循环有重大贡献。
