LEXEN: Interactions Between Hyperthermophilic Communities and Silica Mineralization: Implications for Paleobiology

LEXEN：超嗜热群落与二氧化硅矿化之间的相互作用：对古生物学的影响

• 批准号: 9809471
• 负责人: Sherry Cady
• 金额: $ 30万
• 依托单位: SETI Institute
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-10-15 至 2000-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9809471&HistoricalAwards=false
• 关键词: LEXEN; Interactions; Between; Hyperthermophilic; Communities

9809471CadyHydrothermal deposits that form in the presence of heat-loving microbial communities are analogs for one of Earth's earliest ecosystems. Molecular phylogenetic studies of extant life suggest that these earliest ecosystems were inhabited by hyperthermophiles (optimum growth temperatures 80░C), microorganisms that define life's upper temperature limit. It remains debatable whether life evolved at high temperatures, or whether high temperature microorganisms were the only groups to survive the massive impact events of the 'late bombardment' period. In either case, study of the potential for hydrothermal deposits to serve as important paleobiological repositories supports NSF's goal to understand how the products of early life on Earth are preserved in the geological record. To maximize paleobiological interpretations of hyperthermophilic communities from ancient hydrothermal deposits requires an understanding of the processes by which hyperthermophilic biogenic signatures are initially preserved and subsequently altered by post-depositional diagenetic effects. Biogenic signatures, the products of life that are preserved in the rock record, include microfossils, stromatolites, and chemofossils. The primary objectives of the project are to identify the organosedimentary processes responsible for the preservation of hyperthermophilic biogenic signatures in high-temperature ecosystems, and to document how primary biogenic signatures are altered during early diagenesis.To provide a framework within which the paleobiology of hyperthermophilic communities fossilized in siliceous hydrothermal deposits (thermal spring and especially epithermal deposits) can be properly interpreted, extant communities that occupy silica-depositing thermal springs will be characterized by molecular phylogeny and various electron beam-imaging methods. Hyperthermophilic microfossils that display morphological fidelity will be investigated using spectroscopic imaging, diffraction, and low dose transmission imaging and analytical (EELS/EDS) electron microscopy to identify the mechanisms of fossilization. To establish a baseline survey of the types of unique hyperthermophilic biomarker compounds preserved in natural siliceous hydrothermal deposits, samples with organically preserved hyperthermophilic remains will be analyzed for total organic carbon (TOC), 13C, lipid ratios, and biomarkers. The organosedimentary interactions responsible for the morphological development of high-temperature siliceous sinter stromatolites will be investigated from the submicroscopic to macroscopic scale. Field experiments, designed to produce sequentially biogenic and abiogenic siliceous hydrothermal deposits from natural hydrothermal fluids in a 'water tunnel' will be conducted at a geothermal power station in New Zealand. Direct comparison of biogenic and abiogenic hydrothermal deposits from the submicroscopic to macroscale will provide a robust set of criteria for distinguishing the biogenicity of siliceous hydrothermal precipitates. An improved ability to recognize and confidently assess in the rock record the biogenic signatures of hyperthermophilic communities will advance interpretations of the early fossil record of life on Earth and, potentially, on Mars.

9809471Cady 在喜热微生物群落存在的情况下形成的热液沉积物与地球上最早的生态系统之一类似。对现存生命的分子系统发育研究表明，这些最早的生态系统居住着超嗜热微生物（最适生长温度 80░C），这些微生物定义了生命的存在。生命是否在高温下进化，或者是否在高温下进化，仍然存在争议。微生物是唯一在“晚期轰炸”时期的大规模撞击事件中幸存下来的群体，无论哪种情况，对热液沉积物作为重要古生物学宝库的潜力的研究都支持美国国家科学基金会了解地球早期生命产物的目标。为了最大限度地对古代热液沉积物中的超嗜热生物群落进行古生物学解释，需要了解超嗜热生物特征最初被保存以及随后的过程。生物特征是岩石记录中保存的生命产物，包括微化石、叠层石和化学化石，该项目的主要目标是确定负责保存超高温生物成因的有机沉积过程。高温生态系统中的特征，并记录早期成岩作用期间主要生物特征如何改变。硅质热液沉积物（温泉，尤其是浅成热液沉积物）中形成的超嗜热群落可以得到正确解释，占据二氧化硅沉积热泉的现存群落将通过分子系统发育和各种显示形态保真度的超嗜热微化石进行表征。使用光谱成像、衍射、低剂量透射成像和分析 (EELS/EDS) 电子显微镜进行研究为了确定化石化机制，对天然硅质热液沉积物中保存的独特超高温生物标记化合物类型进行基线调查，将对有机保存的超高温遗迹样品进行总有机碳 (TOC)、13C、脂质比率和有机碳含量分析。将从亚微观到宏观研究负责高温硅质烧结叠层石形态发育的有机沉积相互作用。旨在从“水隧道”中的天然热液流体连续生产生物成因和非生物成因硅质热液沉积物的现场实验将在新西兰的地热发电站进行，从亚微观到宏观尺度直接比较生物成因和非生物成因热液沉积物。将为区分硅质热液沉淀物的生物成因提供一套可靠的标准，提高识别和自信地评估岩石记录中生物成因的能力。超嗜热群落的特征将促进对地球上以及可能在火星上的早期生命化石记录的解释。