Collaborative Research: Characterization of Microbial Transformations in Basement Fluids, from Genes to Geochemical Cycling

目前的估计表明，能够维持生命的海洋地壳的体积与海洋的体积相当。迄今为止，人们对海底微生物群落的组成或功能能力，或它们对海洋化学的影响以及对全球生物地球化学循环的后续后果知之甚少。本项目的重点是了解年轻地壳流体中微生物群落与流体化学之间的关系，这些流体负责地壳中能量、营养物质和生物的运输。具体来说，pi将把微生物活动测量（包括自养碳、氮和硫代谢以及矿物氧化物还原）与功能基因表达和基底流体地球化学转化的定量评估结合起来。通过一套全面的现场和船上分析，这项研究将使我们对海底生物圈的微生物生态学和地球化学的理解取得跨学科的进展。这项工作的重点是在北池，这是一个孤立的沉积物池，位于大西洋中脊西侧的海洋地壳侧面，距今700万至800万年。北池目前是IODP第336次考察的钻探目标，在此期间，它将与三个海底地下室观测站进行仪器测量。该项目将利用这一机会，在两次德美研究巡航中在北池进行有针对性和独特的采样，以实现三个主要目标：确定北池不同的基底流体层是否拥有不同的微生物群落和化学环境，以及它们在钻探后两年期间的变化程度。2 .通过微生物介导的基底流体中碳、氮和硫的转化来量化自养代谢的程度。确定北池基底流体中悬浮颗粒矿物氧化物的程度，并确定其作为流体宿主微生物群落氧化剂的作用。具体结果包括微生物活动和基因表达以及地球化学转化的定量评估。该项目建立在北池综合研究目标的基础上，将为指导北池和未来深层生物圈研究项目的发展提供重要数据。研究结果将增加对年轻海洋地壳微生物生命和化学的认识，并为控制全球海洋微生物群落的分布和活动提供新的见解。更广泛的影响没有关于普遍存在的寒冷海洋地壳中微生物群落的数据，这是拟议工作的重点。这是一个跨学科的项目，在微生物生态学，化学和深海海洋学的界面，与国际和国家的研究和教育组织直接联系。它利用了pi与美国和德国的合作者之间的长期合作，包括最近成立的NSF科学技术中心，名为“暗能量生物圈研究中心”（C-DEBI），以及专注于深层生物圈的NSF研究协调网络。这项关于微生物介导的基底流体地球化学转化的工作是可以实现的，也是及时的，这项工作的方法发展和结果将补充Juan de Fuca Ridge当前和未来的微生物和地球化学研究，作为IODP和OOI区域尺度节点的一部分。公众宣传工作将利用Zephyr教育基金会独特的海洋科学项目，将一个专注于海洋微生物学的短期教育模块纳入其中，该模块将为七年级到大学的学生量身定制。该模块将强调海洋微生物对环境可持续性、人类健康以及地球上生命的起源和进化的重要性。该项目还支持一名研究生、一名本科生和两名博士后的研究和职业发展。学生和博士后将通过新兴和现有的NSF项目与对深层生物圈微生物学和化学感兴趣的更大的研究人员社区进行接触。

Intellectual MeritCurrent estimates suggest that the volume of ocean crust capable of sustaining life is comparable in magnitude to that of the oceans. To date, there is little understanding of the composition or functional capacity of microbial communities in the sub-seafloor, or their influence on the chemistry of the oceans and subsequent consequences for global biogeochemical cycles. This project focuses on understanding the relationship between microbial communities and fluid chemistry in young crustal fluids that are responsible for the transport of energy, nutrients, and organisms in the crust. Specifically, the PIs will couple microbial activity measurements, including autotrophic carbon, nitrogen and sulfur metabolisms as well as mineral oxide reduction, with quantitative assessments of functional gene expression and geochemical transformations in basement fluids. Through a comprehensive suite of in situ and shipboard analyses, this research will yield cross-disciplinary advances in our understanding of the microbial ecology and geochemistry of the sub-seafloor biosphere. The focus of the effort is at North Pond, an isolated sediment pond located on ridge flank oceanic crust 7-8 million years old on the western side of the Mid-Atlantic Ridge. North Pond is currently the target for drilling on IODP expedition 336, during which it will be instrumented with three sub-seafloor basement observatories. The project will leverage this opportunity for targeted and distinct sampling at North Pond on two German-US research cruises to accomplish three main objectives:1. to determine if different basement fluid horizons across North Pond host distinct microbial communities and chemical milieus and the degree to which they change over a two-year post-drilling period.2. to quantify the extent of autotrophic metabolism via microbially-mediated transformations in carbon, nitrogen, and sulfur species in basement fluids at North Pond.3. to determine the extent of suspended particulate mineral oxides in basement fluids at North Pond and to characterize their role as oxidants for fluid-hosted microbial communities.Specific outcomes include quantitative assessments of microbial activity and gene expression as well as geochemical transformations. The program builds on the integrative research goals for North Pond and will provide important data for guiding the development of that and future deep biosphere research programs. Results will increase understanding of microbial life and chemistry in young oceanic crust as well as provide new insights into controls on the distribution and activity of marine microbial communities throughout the worlds oceans.Broader ImpactsThere are no data about microbial communities in ubiquitous cold, oceanic crust, the emphasis of the proposed work. This is an interdisciplinary project at the interface of microbial ecology, chemistry, and deep-sea oceanography with direct links to international and national research and educational organizations. It leverages on a long-term collaboration between the PIs and collaborators in both the US and Germany, including the recently formed NSF Science and Technology Center entitled "Center for Dark Energy Biosphere Investigations" (C-DEBI) and the NSF Research Coordination Network focused on the deep biosphere. This work on microbially mediated geochemical transformations in basement fluids is both attainable and timely, and methods development and results from this work will complement current and future microbial and geochemical investigations on the Juan de Fuca Ridge as part of both IODP and the OOI Regional Scale Node. The public outreach effort will utilize The Zephyr Education Foundation's unique marine science program to incorporate a short educational module focused on marine microbiology that will be tailored to the grade levels 7 through college. The module will emphasize the importance of marine microbes to environmental sustainability, human health, and the origin and evolution of life on our planet. The project also supports the research and career development of one graduate student, one undergraduate student, and two postdoctoral researchers. Students and postdocs will to engage with the larger community of researchers interested in deep biosphere microbiology and chemistry through emerging and existing NSF programs.