The seafloor sulfide structures of inactive vents are known to host abundant and diverse microorganisms potentially supported by mineralogy of sulfides. However, little is known about the diversity and distribution of microbial functions. Here, we used genome-resolved metagenomics to predict microbial metabolic functions and the contribution of horizontal gene transfer to the functionality of microorganisms inhabiting several hydrothermally inactive seafloor deposits among globally distributed deep-sea vent fields. Despite of geographically distant vent fields, similar microbial community patterns were observed with the dominance of Gammaproteobacteria, Bacteroidota and previously overlooked Candidatus Patescibacteria. Metabolically flexible Gammaproteobacteria are major potential primary producers utilizing mainly sulfur, iron and hydrogen as electron donors coupled with oxygen and nitrate respiration for chemolithoautotrophic growth. In addition to heterotrophic microorganisms like free-living Bacteroidota, Ca. Patescibacteria potentially perform fermentative recycling of organic carbon. Finally, we provided evidence that many functional genes that are central to energy metabolism have been laterally transferred among members within the community and largely within the same class. Taken together, these findings shed light on microbial ecology and evolution in inactive seafloor sulfide deposits after the cessation of hydrothermal activities.

中文翻译：

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非活性海底硫化物矿床中微生物群落的功能多样性

众所周知，非活动喷口的海底硫化物结构承载着丰富多样的微生物，可能受到硫化物矿物学的支持。然而，人们对微生物功能的多样性和分布知之甚少。在这里，我们使用基因组解析的宏基因组学来预测微生物代谢功能以及水平基因转移对微生物功能的贡献，这些微生物栖息在全球分布的深海喷口区中的几个热液不活跃海底沉积物中。尽管有地理上遥远的喷口场，但观察到类似的微生物群落模式，主要是Gammaproteobacteria、Bacteroidota 和以前被忽视的Candidatus Patescibacteria。代谢灵活的γ-变形菌是主要的潜在初级生产者，主要利用硫、铁和氢作为电子供体，结合氧和硝酸盐呼吸进行化学自养生长。除了异养微生物如自由生活的拟杆菌外，Ca. Patescibacteria 可能进行有机碳的发酵回收。最后，我们提供的证据表明，许多对能量代谢至关重要的功能基因已在社区内的成员之间横向转移，并且大部分在同一类内。总之，这些发现揭示了热液活动停止后不活跃海底硫化物矿床的微生物生态学和进化。