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

深层地下水环境含有地球生物量的很大一部分，其中的生物体参与碳和其他元素的地球化学循环。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新陈代谢的复制体。该项目的重点是深（3公里），古老（10 - 20亿年），高盐断裂水，通过南非金矿的钻孔进入。在这个系统中的水-岩相互作用有助于增加流体盐度，并产生氢气，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）以及地球生命起源和早期进化的理解。该项目涉及国际合作，将吸引研究生和本科生参与，重点是招募少数/代表性不足的群体。该项目的目标是了解在深层高盐断裂流体环境中发生的约20亿年时间尺度的非生物和生物过程的相互作用。从两个盐水钻孔中的每一个中收集初始的一套样品。将进行进一步抽样。样品的特性鉴定将包括对溶解的和挥发性有机碳化合物进行鉴定和量化，对无机和有机化合物以及断裂矿物进行稳定同位素分析，以及对溶解的惰性气体进行放射性测年。对至少一个钻孔的生物质，除病毒组表征外，还将进行宏基因组学、元转录组学、元蛋白组学和脂质组学分析。1）在生物量丰度极低的更深、更热（55°C）的钻孔中，将首次表征过去数十亿年来水-岩反应形成的非生物有机化合物的清单; 2）在较浅、较冷（48°C）的钻孔中，生物质丰度似乎更大，群落将由非生物成因的烃支持，表现出更高的渗透调节和磷摄取基因表达，并具有其组成提供较低膜渗透性的脂质。该提案的重点是高盐度、水文隔离的深部裂缝流体中的非生物有机地球化学和微生物循环，其直接应用于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，以及对火星和其他行星上现存生命的探索。该奖项反映了NSF的法定使命，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来提供支持。

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.