Caro Tristan A, Kashyap Srishti, Maloney Ashley E, Hoyt David W, Kubo Michael D Y, Hoehler Tori M, Templeton Alexis S
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, USA.
bioRxiv. 2025 Aug 25:2025.08.25.672207. doi: 10.1101/2025.08.25.672207.
Serpentinites, hydrated ultramafic rocks that produce [hyper]alkaline, reducing, H2-rich groundwaters, host subsurface microbial ecosystems. Though in the presence of enormous reducing power, life in serpentinizing systems is limited by oxidant and carbon availability. The forms of carbon that support the serpentinite-hosted microbiome, and their rates of biological assimilation, remain poorly understood. In this work, we quantify the habitability of subsurface environments shaped by serpentinization and examine the forms of carbon that support their microbial constituents, focusing specifically on dissolved inorganic carbon, acetate, and formate. We access reacted groundwater from Earth's largest terrestrial serpentinizing body and measure carbon assimilation at the single-cell level. Across all conditions, we consistently observe robust assimilation of dissolved inorganic carbon into microbial biomass. Notably, we find that dissolved inorganic carbon supports the majority of methanogenic activity in the system, even at hyperalkaline conditions (pH > 11). Inferred bioenergetic fluxes suggest that rates of biological hydrogen-consumption and methanogenesis are relevant at the landscape scale. We identify a strong potential for the microbiome to be stimulated by increases in H and CO, a finding with implications for the search for life on other planetary bodies and for the growing deployment of fluid injection technologies in ultramafic rocks, such as geological hydrogen production or carbon mineralization.
蛇纹岩是一种水化超镁铁岩，能产生[超]碱性、具有还原性且富含氢气的地下水，其中存在着地下微生物生态系统。尽管蛇纹石化系统具有巨大的还原能力，但其中的生命却受到氧化剂和碳可用性的限制。目前，对于支持蛇纹岩中微生物群落的碳形式及其生物同化速率，我们仍知之甚少。在这项研究中，我们量化了由蛇纹石化作用塑造的地下环境的宜居性，并研究了支持其微生物组成的碳形式，特别关注溶解无机碳、乙酸盐和甲酸盐。我们获取了来自地球上最大的陆地蛇纹石化岩体的反应后地下水，并在单细胞水平上测量了碳同化情况。在所有条件下，我们始终观察到溶解无机碳被强劲地同化为微生物生物量。值得注意的是，我们发现即使在超碱性条件（pH > 11）下，溶解无机碳仍支持系统中大部分的产甲烷活动。推断出的生物能通量表明，生物氢消耗和产甲烷速率在景观尺度上具有相关性。我们发现微生物群落具有被氢气和一氧化碳增加所刺激的强大潜力，这一发现对于在其他行星体上寻找生命以及在超镁铁岩中日益广泛应用的流体注入技术（如地质制氢或碳矿化）具有重要意义。
