Collaborative Research: Biogeochemical Processes in a Subsurface Hypersaline Environment near the Abiotic Fringe

深层地下水环境包含了地球生物量的很大一部分，其中的生物参与了碳和其他元素的生物地球化学循环。它们也是生命起源的候选环境之一，即从简单的非生物化学反应过渡到细胞的、代谢的、复制的环境。该项目的重点是通过南非金矿的钻孔获取深层（3公里）、古老（10 - 10亿年）、高盐裂缝水。该体系中的水岩相互作用增加了流体盐度，并产生了氢气、甲烷、其他短链烃和简单的碳硫化合物，这些化合物可能是生命的重要前体。该项目将促进对碳循环、含盐地下水（与石油储层直接相关）以及地球上生命的起源和早期进化的理解。该项目涉及国际合作，将招收研究生和本科生，重点是招收少数民族/代表性不足的群体。该项目的目标是了解发生在深部高盐压裂流体环境中超过20亿年时间尺度的非生物和生物过程的相互作用。从两个盐水井中各收集了一套初始样品。我们会进行进一步抽样。样品的表征将包括溶解和挥发性有机碳化合物的鉴定和定量，无机和有机化合物以及断裂矿物的稳定同位素分析，以及溶解惰性气体的放射性测年。对至少一个井眼的生物量，将进行宏基因组学、宏转录组学、宏蛋白质组学和脂质组学分析，以及病毒组表征。以下假设将得到验证：1)在更深、更热（55°C）、生物量丰度极低的钻孔中，由过去数十亿年的水岩反应形成的非生物有机化合物的清单将首次被表征；2)在较浅、较冷（48°C）的钻孔中，生物量丰度较高，群落以非生物源烃类为支撑，渗透调节基因和磷吸收基因表达较多，脂质成分提供较低的膜通透性。本研究的重点是非生物有机地球化学和微生物循环在高盐、水文隔离、深层裂缝流体中的应用，对全球重要的前寒武纪水文储层、石油矿床的生物降解、地下生命的起源和演化，以及火星和其他行星体上现存生命的探索具有直接的应用价值。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Deep groundwater environments contain a significant portion of Earth's biomass and the organisms therein participate in biogeochemical cycling of carbon and other elements. They are also among the candidate environments for the origin of life, i.e., for the transition from simple, abiotic chemical reactions to cellular, metabolic, replicants. This project is focused on deep (3km), ancient (1-2 billion-year-old), hypersaline fracture water, accessed via boreholes in a South African gold mine. Water-rock interactions in this system contribute to increased fluid salinity and generate hydrogen gas, methane, other short-chain hydrocarbons, and simple carbon-sulfur compounds that may be important precursors to life. This project will advance understanding of carbon cycling, saline groundwater (directly relevant to petroleum reservoirs), and the origin and early evolution of life on Earth. The project involves international collaboration and will engage both graduate and undergraduate students, with emphasis on recruiting minority/underrepresented groups.The goal of this project is to understand the interactions of abiotic and biotic processes occurring over a ~2-billion-year time scale in deep hypersaline fracture fluid environments. An initial suite of samples was collected from each of two brine boreholes. Further sampling will be conducted. Characterization of the samples will include identification and quantification of dissolved and volatile organic carbon compounds, stable isotopic analyses of inorganic and organic compounds and of fracture minerals, and radiometric dating of dissolved noble gases. On the biomass of at least one borehole, metagenomic, metatranscriptomic, metaproteomic, and lipidomic analyses, in addition to virome characterization, will be performed. The following hypotheses will be tested: 1) In the deeper, hotter (55°C) borehole where the biomass abundance is extremely low, an inventory of abiotic organic compounds formed by water-rock reactions over the past billions of years will be characterized for the first time; 2) In the shallower, cooler (48°C) borehole where the biomass abundance appears greater, the community will be supported by abiogenic hydrocarbons, exhibit a greater expression of osmotic regulation and phosphorous uptake genes, and possess lipids whose composition provide lower membrane permeability. This proposal's focus on the abiotic organic geochemistry and microbial cycling in hypersaline, hydrologically isolated, deep fracture fluids has direct applications to globally significant Precambrian hydrologic reservoirs, biodegradation of petroleum deposits, the origins and evolution of life in the subsurface, and the exploration for extant life on Mars and other planetary bodies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.