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、代谢、复制体的环境。该项目的重点是深水(3公里)、古老(10-20亿年)、高盐度裂隙水，通过南非金矿的钻孔进入。在这个系统中，水-岩石的相互作用有助于增加流体盐度，并产生氢气、甲烷、其他短链碳氢化合物和简单的碳硫化合物，这些可能是生命的重要前身。该项目将促进对碳循环、含盐地下水(与石油储藏直接相关)以及地球上生命的起源和早期演化的理解。该项目涉及国际合作，将吸引研究生和本科生，重点是招收少数族裔/代表性不足的群体。该项目的目标是了解在20亿年的时间尺度上发生的非生物和生物过程在深度高盐度压裂流体环境中的相互作用。最初的一套样品是从两个盐水钻孔中分别采集的。将会进行进一步的抽样。样品的特征将包括对溶解和挥发的有机碳化合物进行鉴定和量化，对无机和有机化合物以及裂解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。除了对病毒体进行鉴定外，还将对至少一个钻孔的生物量进行元基因组、元转录组学、元蛋白质组和脂体学分析。将检验下列假设：1)在生物量丰度极低的更深、更热(55℃)的钻孔中，将首次描述过去数十亿年水-岩反应形成的非生物有机化合物的清单；2)在生物量丰度显示更大的更浅、更冷(48℃)的钻孔中，群落将得到非生物碳氢化合物的支持，表现出更多渗透调节和磷吸收基因的表达，并具有组成成分提供较低膜通透性的脂类。这项提议的重点是高盐度、水文隔离、深层裂隙流体中的非生物有机地球化学和微生物循环，直接应用于全球重要的前寒武纪水文水库、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有生命的勘探。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.