Collaborative Research: Investigating the Lost City as an ultramafic urban center of the subseafloor, fueled by energy and carbon from the mantle

合作研究：调查失落之城是海底超镁铁质城市中心，以地幔能量和碳为燃料

• 批准号: 1536405
• 负责人: William Brazelton
• 金额: $ 25.96万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1536405&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Lost; City

The vast majority of deep seafloor sediments are inhabited by microbial communities that survive under extreme energy limitation, with apparent generation times of centuries to millennia. Hydrothermal systems are a stark contrast to these energy-starved environments and may represent important, high-activity, 'population centers' in the oceanic subsurface. When rocks from the Earth's mantle are uplifted and exposed to water, the resulting reactions lead to acidic fluids with high concentrations of hydrogen. Under certain circumstances, small organic molecules such as methane can also form in the absence of biology. These compounds can provide energy to subseafloor microbial communities and, given the ubiquity of mantle rocks, such reactions may fuel a significant proportion of the active subsurface biosphere. The current project will characterize the microbial communities inhabiting an iconic example of this type of system, the Lost City Hydrothermal Field, using a remotely operated vehicle. The ghostly spires of Lost City are highly telegenic and have been featured in professional documentaries. The high definition underwater video footage collected during the expedition will provide the raw material for an 8 week educational training program in digital media focused on kindergarten through 12th grade high school students and undergraduate students. The resulting short documentaries will be published on YouTube and the Utah Education Network.Mantle rocks comprise significant portions of the seafloor, and microbial communities hosted within them may be important mediators of carbon and energy exchange between the deep Earth and the surface biosphere. Upon tectonic uplift and exposure to water, the serpentinization of these materials releases potential energy in the form of hydrogen, methane, and heat, and further reaction of these products can sustain the abiogenic synthesis of small organic molecules. Recent studies have highlighted, however, the lack of alkalithermophiles that are capable of survival at the high pH (9-11) and elevated temperatures found in these systems. The almost complete lack of carbon dioxide (CO2) represents a second, and possibly more significant, limitation to growth. To better understand the extent of the serpentinite subsurface, this project will address the question: What limits biological activity in the serpentinite subsurface? Specifically, the proposed work will test the hypotheses: (1) microbial diversity spans a wider range of temperature-pH conditions than currently recognized and (2) the scarcity of CO2 is a key biological limitation to serpentinization-driven ecosystems that can be overcome by the metabolic activity of one or a few foundation species. These hypotheses will be tested during a 20 day (10 days on site) expedition to the Lost City Hydrothermal Field, focusing on fluids as windows to the subsurface biosphere. The sampling approach will capitalize on the differences in temperature, carbon availability, and microbial activity across the field. The analytical approach will integrate multidisciplinary techniques performed on replicate subsamples and feature the application of next-generation sequencing technologies to these marine serpentinizing fluids for the first time. This study will generate extensive sequence data from environmental DNA, environmental mRNA, and single-cell genomes, allowing us to identify the in situ expression of metabolic pathways and the genomics of active single cells. These efforts will be closely linked with a thorough characterization of carbon in these fluids that will focus on identifying available substrates (e.g. methane, CO2, organic acids) and on characterizing biomarkers that reflect specific metabolic pathways (e.g. lipids, amino acids).

绝大多数深海海底沉积物都居住着微生物群落，它们在极端的能量限制下生存，明显的一代周期为数百年至数千年。热液系统与这些能源匮乏的环境形成鲜明对比，可能代表了海洋地下重要的、高活动的“人口中心”。当地幔中的岩石被抬升并暴露在水中时，由此产生的反应会产生含有高浓度氢的酸性流体。在某些情况下，甲烷等小有机分子也可以在没有生物的情况下形成。这些化合物可以为海底微生物群落提供能量，鉴于地幔岩石的普遍存在，这些反应可能会为很大一部分活跃的地下生物圈提供能量。目前的项目将使用远程操作的工具来描述居住在这类系统的一个标志性例子——失落之城热液场的微生物群落。失落之城幽灵般的塔尖非常上镜，并在专业纪录片中出现过。在探险期间收集的高清水下视频片段将为为期8周的数字媒体教育培训计划提供原材料，重点是幼儿园到12年级的高中生和本科生。由此产生的短纪录片将在YouTube和犹他教育网上发布。地幔岩是海底的重要组成部分，其中的微生物群落可能是深层地球和表层生物圈之间碳和能量交换的重要媒介。在构造抬升和遇水作用下，这些物质的蛇纹岩化作用以氢、甲烷和热的形式释放势能，这些产物的进一步反应可以维持小有机分子的非生物合成。然而，最近的研究强调，缺乏能够在这些系统中发现的高pH值（9-11）和高温下存活的嗜碱热微生物。几乎完全缺乏二氧化碳（CO2）代表了第二个，可能是更重要的，对生长的限制。为了更好地了解蛇纹岩地下的范围，该项目将解决以下问题：是什么限制了蛇纹岩地下的生物活动？具体来说，拟议的工作将验证以下假设：(1)微生物多样性跨越的温度- ph条件范围比目前认识到的更广；(2)二氧化碳的稀缺性是蛇形化驱动的生态系统的关键生物学限制，可以通过一种或几种基础物种的代谢活动来克服。这些假设将在为期20天（现场10天）的失落之城热液场考察中得到验证，重点关注流体作为地下生物圈的窗口。采样方法将利用温度、碳可用性和整个油田微生物活动的差异。该分析方法将整合多学科技术，对重复亚样本进行分析，并首次将下一代测序技术应用于这些海洋蛇纹石化流体。本研究将从环境DNA、环境mRNA和单细胞基因组中获得广泛的序列数据，使我们能够识别代谢途径的原位表达和活性单细胞的基因组学。这些工作将与对这些流体中碳的全面表征密切相关，重点是确定可用的底物（如甲烷、二氧化碳、有机酸）和表征反映特定代谢途径的生物标志物（如脂质、氨基酸）。