Sabuda Mary C, Brazelton William J, Putman Lindsay I, McCollom Tom M, Hoehler Tori M, Kubo Michael D Y, Cardace Dawn, Schrenk Matthew O
Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI, 48824, USA.
Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA.
Environ Microbiol. 2020 Jun;22(6):2329-2345. doi: 10.1111/1462-2920.15006. Epub 2020 Apr 21.
Serpentinization is the hydration and oxidation of ultramafic rock, which occurs as oceanic lithosphere is emplaced onto continental margins (ophiolites), and along the seafloor as faulting exposes this mantle-derived material to circulating hydrothermal fluids. This process leads to distinctive fluid chemistries as molecular hydrogen (H ) and hydroxyl ions (OH ) are produced and reduced carbon compounds are mobilized. Serpentinizing ophiolites also serve as a vector to transport sulfur compounds from the seafloor onto the continents. We investigated hyperalkaline, sulfur-rich, brackish groundwater in a serpentinizing continental ophiolite to elucidate the role of sulfur compounds in fuelling in situ microbial activities. Here we illustrate that key sulfur-cycling taxa, including Dethiobacter, Desulfitispora and 'Desulforudis', persist throughout this extreme environment. Biologically catalysed redox reactions involving sulfate, sulfide and intermediate sulfur compounds are thermodynamically favourable in the groundwater, which indicates they may be vital to sustaining life in these characteristically oxidant- and energy-limited systems. Furthermore, metagenomic and metatranscriptomic analyses reveal a complex network involving sulfate reduction, sulfide oxidation and thiosulfate reactions. Our findings highlight the importance of the complete inorganic sulfur cycle in serpentinizing fluids and suggest sulfur biogeochemistry provides a key link between terrestrial serpentinizing ecosystems and their submarine heritage.
蛇纹石化作用是超镁铁质岩石的水化和氧化过程，它发生在海洋岩石圈就位到大陆边缘（蛇绿岩）时，以及沿着海底，断层作用使这种源自地幔的物质暴露于循环的热液流体中。这个过程会产生独特的流体化学性质，因为会产生分子氢（H）和氢氧根离子（OH），并使还原态碳化合物发生迁移。蛇纹石化的蛇绿岩还充当了将硫化合物从海底输送到大陆的载体。我们研究了蛇纹石化大陆蛇绿岩中高碱性、富含硫的微咸地下水，以阐明硫化合物在促进原位微生物活动中的作用。在此我们表明，包括脱硫杆菌属、脱硫孢菌属和“脱硫嗜铁菌属”在内的关键硫循环类群在这种极端环境中持续存在。涉及硫酸盐、硫化物和中间硫化合物的生物催化氧化还原反应在地下水中在热力学上是有利的，这表明它们对于维持这些典型的氧化剂和能量受限系统中的生命可能至关重要。此外，宏基因组和宏转录组分析揭示了一个涉及硫酸盐还原、硫化物氧化和硫代硫酸盐反应的复杂网络。我们的研究结果突出了完整的无机硫循环在蛇纹石化流体中的重要性，并表明硫生物地球化学提供了陆地蛇纹石化生态系统与其海底起源之间的关键联系。
