Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China.
School of Marine Sciences, Sun Yat-Sen University, Zhuhai, China.
Nat Commun. 2022 Aug 19;13(1):4885. doi: 10.1038/s41467-022-32503-w.
Microbially mediated nitrogen cycling in carbon-dominated cold seep environments remains poorly understood. So far anaerobic methanotrophic archaea (ANME-2) and their sulfate-reducing bacterial partners (SEEP-SRB1 clade) have been identified as diazotrophs in deep sea cold seep sediments. However, it is unclear whether other microbial groups can perform nitrogen fixation in such ecosystems. To fill this gap, we analyzed 61 metagenomes, 1428 metagenome-assembled genomes, and six metatranscriptomes derived from 11 globally distributed cold seeps. These sediments contain phylogenetically diverse nitrogenase genes corresponding to an expanded diversity of diazotrophic lineages. Diverse catabolic pathways were predicted to provide ATP for nitrogen fixation, suggesting diazotrophy in cold seeps is not necessarily associated with sulfate-dependent anaerobic oxidation of methane. Nitrogen fixation genes among various diazotrophic groups in cold seeps were inferred to be genetically mobile and subject to purifying selection. Our findings extend the capacity for diazotrophy to five candidate phyla (Altarchaeia, Omnitrophota, FCPU426, Caldatribacteriota and UBA6262), and suggest that cold seep diazotrophs might contribute substantially to the global nitrogen balance.
微生物介导的碳主导型冷渗环境中的氮循环仍知之甚少。到目前为止，已在深海冷渗沉积物中鉴定出厌氧甲烷营养古菌（ANME-2）及其硫酸盐还原细菌伙伴（SEEP-SRB1 进化枝）为固氮生物。然而，其他微生物群是否能够在这样的生态系统中进行固氮仍不清楚。为了填补这一空白，我们分析了来自 11 个全球分布的冷渗区的 61 个宏基因组、1428 个宏基因组组装基因组和 6 个宏转录组。这些沉积物中含有与扩展的固氮生物谱系多样性相对应的系统发育多样的固氮酶基因。预测多种分解代谢途径可为固氮提供 ATP，表明冷渗中的固氮作用不一定与依赖硫酸盐的甲烷厌氧氧化有关。推断冷渗中各种固氮生物群的固氮基因具有遗传可移动性，并受到纯化选择的影响。我们的研究结果将固氮能力扩展到了五个候选门（古菌门、全氮营养菌门、FCPU426 门、Caldatribacteriota 门和 UBA6262 门），并表明冷渗固氮生物可能对全球氮平衡有很大贡献。
