Thermodynamic models predict that H₂ is energetically favorable for seafloor microbial life, but how H₂ affects anabolic processes in seafloor-associated communities is poorly understood. Here, we used quantitative ¹³C DNA stable isotope probing (qSIP) to quantify the effect of H₂ on carbon assimilation by microbial taxa synthesizing ¹³C-labeled DNA that are associated with partially serpentinized peridotite rocks from the equatorial Mid-Atlantic Ridge. The rock-hosted seafloor community was an order of magnitude more diverse compared to the seawater community directly above the rocks. With added H₂, peridotite-associated taxa increased assimilation of ¹³C-bicarbonate and ¹³C-acetate into 16S rRNA genes of operational taxonomic units by 146% (±29%) and 55% (±34%), respectively, which correlated with enrichment of H₂-oxidizing NiFe-hydrogenases encoded in peridotite-associated metagenomes. The effect of H₂ on anabolism was phylogenetically organized, with taxa affiliated with Atribacteria, Nitrospira, and Thaumarchaeota exhibiting the most significant increases in ¹³C-substrate assimilation in the presence of H₂. In SIP incubations with added H₂, an order of magnitude higher number of peridotite rock-associated taxa assimilated ¹³C-bicarbonate, ¹³C-acetate, and ¹³C-formate compared to taxa that were not associated with peridotites. Collectively, these findings indicate that the unique geochemical nature of the peridotite-hosted ecosystem has selected for H₂-metabolizing, rock-associated taxa that can increase anabolism under high H₂ concentrations. Because ultramafic rocks are widespread in slow-, and ultraslow-spreading oceanic lithosphere, continental margins, and subduction zones where H₂ is formed in copious amounts, the link between H₂ and carbon assimilation demonstrated here may be widespread within these geological settings.

热力学模型预测，H ₂在能量上对海底微生物生命有利，但人们对 H ₂如何影响海底相关群落的合成代谢过程知之甚少。在这里，我们使用定量¹³ C DNA 稳定同位素探测 (qSIP) 来量化 H ₂对通过微生物类群合成¹³ C 标记的 DNA 对碳同化的影响，这些 DNA 与来自赤道中大西洋海脊的部分蛇纹石化橄榄岩岩石相关。与岩石正上方的海水群落相比，以岩石为主体的海底群落的多样性要高出一个数量级。添加 H ₂后，橄榄岩相关分类群增加了¹³C-碳酸氢盐和¹³ C-乙酸盐分别以 146% (±29%) 和 55% (±34%) 进入可操作分类单位的 16S rRNA 基因，这与橄榄岩中编码的 H ₂氧化性NiFe-氢化酶的富集相关相关的宏基因组。H ₂对合成代谢的影响是系统发育组织的，与Atribacteria、Nitrospira和 Thaumarchaeota 相关的分类群在 H _{2存在下表现出}¹³ C-底物同化的最显着增加。在添加 H _{2的 SIP 孵化中，橄榄岩岩石相关类群同化}¹³ C-碳酸氢盐的数量要高一个数量级，¹³ C-乙酸盐和¹³ C-甲酸盐与与橄榄岩无关的分类群相比。总的来说，这些发现表明橄榄岩生态系统的独特地球化学性质选择了在高 H ₂浓度下可以增加合成代谢的 H _{2代谢、岩石相关类群。}由于超镁铁岩广泛分布于缓慢和超缓慢扩展的海洋岩石圈、大陆边缘和俯冲带，在这些带中形成大量 H 2 ，因此此处证明的 H 2 与碳同化之间的联系_可能在这些地质环境中广泛存在。