Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA.
NASA Astrobiology Institute, Mountain View, CA, USA.
ISME J. 2019 Jul;13(7):1750-1762. doi: 10.1038/s41396-019-0391-2. Epub 2019 Mar 12.
Hydration of ultramafic rock during the geologic process of serpentinization can generate reduced substrates that microorganisms may use to fuel their carbon and energy metabolisms. However, serpentinizing environments also place multiple constraints on microbial life by generating highly reduced hyperalkaline waters that are limited in dissolved inorganic carbon. To better understand how microbial life persists under these conditions, we performed geochemical measurements on waters from a serpentinizing environment and subjected planktonic microbial cells to metagenomic and physiological analyses. Metabolic potential inferred from metagenomes correlated with fluid type, and genes involved in anaerobic metabolisms were enriched in hyperalkaline waters. The abundance of planktonic cells and their rates of utilization of select single-carbon compounds were lower in hyperalkaline waters than alkaline waters. However, the ratios of substrate assimilation to dissimilation were higher in hyperalkaline waters than alkaline waters, which may represent adaptation to minimize energetic and physiologic stress imposed by highly reducing, carbon-limited conditions. Consistent with this hypothesis, estimated genome sizes and average oxidation states of carbon in inferred proteomes were lower in hyperalkaline waters than in alkaline waters. These data suggest that microorganisms inhabiting serpentinized waters exhibit a unique suite of physiological adaptations that allow for their persistence under these polyextremophilic conditions.
超镁铁质岩石在蛇纹石化地质过程中的水合作用会产生还原基质，微生物可能利用这些基质来驱动其碳和能量代谢。然而，蛇纹石化环境还通过产生高度还原的强碱性水来限制微生物的生存，因为这种水的溶解无机碳含量有限。为了更好地理解微生物在这些条件下是如何生存的，我们对蛇纹石化环境中的水进行了地球化学测量，并对浮游微生物细胞进行了宏基因组学和生理学分析。宏基因组推断出的代谢潜能与流体类型相关，而参与厌氧代谢的基因在强碱性水中富集。与碱性水相比，浮游细胞的丰度和它们对选定的单碳化合物的利用速率在强碱性水中较低。然而，强碱性水中的底物同化与异化的比值高于碱性水中，这可能代表了一种适应策略，以最大限度地减少由高度还原和碳限制条件带来的能量和生理压力。与这一假设一致的是，推断的蛋白质组中估计的基因组大小和碳的平均氧化态在强碱性水中均低于碱性水中。这些数据表明，栖息在蛇纹石化水中的微生物表现出独特的一系列生理适应，使它们能够在这些多极端环境条件下生存。
