Nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) is critical for mitigating methane emission and returning reactive nitrogen to the atmosphere. The genomes of n-DAMO archaea show that they have the potential to couple anaerobic oxidation of methane to dissimilatory nitrate reduction to ammonium (DNRA). However, physiological details of DNRA for n-DAMO archaea were not reported yet. This work demonstrated n-DAMO archaea coupling the anaerobic oxidation of methane to DNRA, which fueled Anammox in a methane-fed membrane biofilm reactor with nitrate as only electron acceptor. Microelectrode analysis revealed that ammonium accumulated where nitrite built up in the biofilm. Ammonium production and significant upregulation of gene expression for DNRA were detected in suspended n-DAMO culture with nitrite exposure, indicating that nitrite triggered DNRA by n-DAMO archaea. ¹⁵N-labeling batch experiments revealed that n-DAMO archaea produced ammonium from nitrate rather than from external nitrite. Localized gradients of nitrite produced by n-DAMO archaea in biofilms induced ammonium production via the DNRA process, which promoted nitrite consumption by Anammox bacteria and in turn helped n-DAMO archaea resist stress from nitrite. As biofilms predominate in various ecosystems, anaerobic oxidation of methane coupled with DNRA could be an important link between the global carbon and nitrogen cycles that should be investigated in future research.

中文翻译：

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甲烷的厌氧氧化与硝酸盐异化还原成氨燃料厌氧铵氧化

硝酸盐/亚硝酸盐依赖性厌氧甲烷氧化（n-DAMO）对于缓解甲烷排放并使活性氮返回大气至关重要。n-DAMO古细菌的基因组表明，它们具有将甲烷的厌氧氧化与硝酸盐还原成铵（DNRA）的潜力。然而，尚未报道DNRA用于n-DAMO古细菌的生理学细节。这项工作证明了n-DAMO古细菌将甲烷的厌氧氧化与DNRA耦合，从而在以硝酸盐为唯一电子受体的甲烷饲喂膜生物膜反应器中为Anammox提供燃料。微电极分析表明，铵盐在生物膜中亚硝酸盐积累的地方积累。在亚硝酸盐接触的悬浮n-DAMO培养物中检测到DNRA的铵生成和基因表达的显着上调，^15个N标记批处理实验表明，n-DAMO古细菌是从硝酸盐而不是外部亚硝酸盐中产生铵的。n-DAMO古细菌在生物膜中产生的亚硝酸盐的局部梯度会通过DNRA过程诱导铵的生成，这会促使Anammox细菌消耗亚硝酸盐，进而帮助n-DAMO古细菌抵抗亚硝酸盐的胁迫。由于生物膜在各种生态系统中占主导地位，甲烷的厌氧氧化与DNRA结合可能是全球碳循环和氮循环之间的重要联系，应在以后的研究中进行研究。