Microbial Activities in Deep-Subsurface Sediments Beneath Mid-Ocean Gyres

人们对地下生命的性质知之甚少。海洋环流是地球上主要的海洋学省份，但这些低营养开阔海洋区域下的海底被勘探得最少。大多数海底调查都集中在大陆边缘附近的高生产率地区。该项目建议使用创新和实验的稳定和放射性同位素方法来研究南太平洋低营养环流和南大西洋环流下的低营养海底沉积物中关键化合物(C，N，O)的代谢活动和生物地球化学循环。智力优势：该建议的主要目标是确定代谢活动(有氧呼吸、异养/自养)，并使用敏感的稳定和放射性同位素方法、细胞提取和单细胞分析(包括纳米级二次质谱分析)来跟踪C、N和P的固定和周转的潜在途径。基本目标是记录地下生境条件和微生物代谢活动的地理变化，并测试控制这些活动的因素。拟议的研究将在(A)海洋区域(大西洋和太平洋的环流中心到环流边缘)、沉积物深度和c)与下面玄武岩过程的关系的比较中测试和量化异养和自养新陈代谢。这项研究将解决海底以下调查中的关键问题：公海海底以下沉积物中的主要微生物活动是什么？新陈代谢能量的主要来源是什么？这些活动的费率是多少？拟议的调查结果将对深层生物圈微生物生态学和生物地球化学领域产生重大影响，因为它们将极大地促进我们对可能代表海底主要区域的地下生物群的了解。更广泛的影响：一名博士后研究员将参与该项目，并将接受研究、指导和职业准备方面的培训。这个项目将吸引将参与研究的本科生。拟议的研究直接支持和推进了对IODP探险329次(南太平洋环流)和336次(南大西洋环流)的大笔投资，这两次探险的重点是地下微生物学。该项目将加强IODP科学家之间的国际合作，包括与设在德国不来梅的MPI的密切合作。南加州大学国家科学基金会暗能量生物圈研究中心(C-DEBI)为教师、K-12学生、本科生和研究生以及博士后研究人员提供教育机会，以培养下一代深海海底生物圈研究人员，并将深层生物圈研究领域的知识转化为更广泛的公众。

The nature of subsurface life is very poorly known. Ocean gyres are the major oceanographic provinces on our planet but the seafloor underlying these oligotrophic open ocean regions is the least explored. Most sub-seafloor investigations have focused on high productivity regions near continental margins. This project proposes to use innovative and experimental stable and radio - isotopiv approaches to address the metabolic activity and the biogeochemical cycling of key compounds (C, N, O) in oligotrophic sub-seafloor sediments underlying the oligotrophic South Pacific Gyre and South Atlantic Gyre.Intellectual Merit: The primary objectives of this proposal are to determine metabolic activities (aerobic respiration, heterotrophy/autotrophy) and to track potential routes of C, N and P fixation and turnover using sensitive stable and radioisotope methods, cell extractions and single cell analyses including nano-scale secondary mass spectrometry (nanoSIMS). The fundamental goals are to document geographic variation in subsurface habitat conditions and microbial metabolic activities and to test the factors controlling those activities. The proposed study will test for and quantify heterotrophic and autotrophic metabolisms in a comparison of (a) ocean regions (gyre center to gyre margin in both the Atlantic and Pacific), b) sediment depth and c) relation to processes in the underlying basalt. This research will addresses key questions in sub-seafloor investigations: What are the principal microbial activities in open ocean sub-seafloor sediments? What are the principal sources of metabolic energy? What are the rates of these activities? The results of the proposed investigations will be transformative to the fields of deep-biosphere microbial ecology and biogeochemistry, as they will significantly advance our understanding of the subsurface biome that may be representative for major areas of the ocean floor. Broader Impacts: One postdoctoral fellow will take part in this project and will receive training in research, mentoring, and career preparation. This project will engage undergraduate students who will participate in the research. The proposed research is directly in support and advances large investments made for IODP expeditions 329 (South Pacific Gyre) and 336 (South Atlantic Gyre), which have a unique focus on subsurface microbiology. This project will strengthen international collaborations between IODP scientists and includes close collaborations with the MPI in Bremen, Germany. The NSF Center for Dark Energy Biosphere Investigations at USC (C-DEBI) provides educational opportunities for teachers, K-12 students, undergraduate and graduate students, as well as post-doctoral researchers to train with the aim to foster the next generation of deep subseafloor biosphere researchers, as well as to translate knowledge in the field of deep biosphere research to the broader public.