Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
Nature. 2013 Aug 29;500(7464):567-70. doi: 10.1038/nature12375. Epub 2013 Jul 28.
Anaerobic oxidation of methane (AOM) is critical for controlling the flux of methane from anoxic environments. AOM coupled to iron, manganese and sulphate reduction have been demonstrated in consortia containing anaerobic methanotrophic (ANME) archaea. More recently it has been shown that the bacterium Candidatus 'Methylomirabilis oxyfera' can couple AOM to nitrite reduction through an intra-aerobic methane oxidation pathway. Bioreactors capable of AOM coupled to denitrification have resulted in the enrichment of 'M. oxyfera' and a novel ANME lineage, ANME-2d. However, as 'M. oxyfera' can independently couple AOM to denitrification, the role of ANME-2d in the process is unresolved. Here, a bioreactor fed with nitrate, ammonium and methane was dominated by a single ANME-2d population performing nitrate-driven AOM. Metagenomic, single-cell genomic and metatranscriptomic analyses combined with bioreactor performance and (13)C- and (15)N-labelling experiments show that ANME-2d is capable of independent AOM through reverse methanogenesis using nitrate as the terminal electron acceptor. Comparative analyses reveal that the genes for nitrate reduction were transferred laterally from a bacterial donor, suggesting selection for this novel process within ANME-2d. Nitrite produced by ANME-2d is reduced to dinitrogen gas through a syntrophic relationship with an anaerobic ammonium-oxidizing bacterium, effectively outcompeting 'M. oxyfera' in the system. We propose the name Candidatus 'Methanoperedens nitroreducens' for the ANME-2d population and the family Candidatus 'Methanoperedenaceae' for the ANME-2d lineage. We predict that 'M. nitroreducens' and other members of the 'Methanoperedenaceae' have an important role in linking the global carbon and nitrogen cycles in anoxic environments.
厌氧甲烷氧化（AOM）对于控制缺氧环境中甲烷通量至关重要。在包含厌氧甲烷氧化古菌（ANME）的共生体中，已经证明了 AOM 与铁、锰和硫酸盐还原偶联。最近，研究表明，细菌“Methylomirabilis oxyfera”可以通过有氧甲烷氧化途径将 AOM 与亚硝酸盐还原偶联。能够进行 AOM 与反硝化偶联的生物反应器导致了“M. oxyfera”和一种新型 ANME 谱系 ANME-2d 的富集。然而，由于“M. oxyfera”可以独立地将 AOM 与反硝化偶联，因此 ANME-2d 在该过程中的作用尚未解决。在这里，一个以硝酸盐、铵盐和甲烷为食的生物反应器被一个单一的 ANME-2d 种群所主导，该种群通过硝酸盐驱动的 AOM 来执行。宏基因组、单细胞基因组和宏转录组分析，结合生物反应器性能和（13）C 和（15）N 标记实验表明，ANME-2d 能够通过以硝酸盐为末端电子受体的反向产甲烷作用独立地进行 AOM。比较分析表明，硝酸盐还原基因是从一个细菌供体横向转移而来的，这表明在 ANME-2d 中选择了这种新过程。ANME-2d 产生的亚硝酸盐通过与厌氧氨氧化细菌的共生关系被还原为氮气气体，有效地在系统中胜过“M. oxyfera”。我们建议将 ANME-2d 种群命名为“Candidatus 'Methanoperedens nitroreducens'”，并将 ANME-2d 谱系命名为“Candidatus 'Methanoperedenaceae'”。我们预测，“M. nitroreducens”和“Methanoperedenaceae”的其他成员在连接缺氧环境中的全球碳氮循环方面具有重要作用。
