COLLABORATIVE RESEARCH: Microbiology and Biogeochemistry of Autotrophic Microbes in the Subsurface at Hydrothermal Vents: Filamentous-Sulfur Producing Bacteria

最近在深海海底发现的微生物种群在生物学上具有深远的意义，并对各种生物地球化学过程产生潜在的重大影响。通过海洋地壳内的裂缝和孔隙流动的热液流体为海底生物群落提供了潜在的丰富环境。最近发表的几项关于微生物喷发的观察指出，海底下生物圈的存在可能对这些热液系统的生产力有很大贡献：9 ° N东太平洋海隆）释放出大量的白色絮状物质，这些物质积累成5 cm厚的垫。这种物质后来被鉴定为由弓形杆菌属的新型微生物产生的丝状硫。PI计划对这些产硫微生物的丰度、分布和多样性进行综合微生物和地球化学研究，并评估它们在9 ° N EPR的生态作用。以前的观测和观测喷发事件与地下生物量产出的高可能性意味着这个网站非常适合解决这些问题。拟议的研究将测试以下一般假设：1）形成强硫的微生物的主要栖息地是浅层地下，即，以热液与海水活跃混合为特征的地下部分以及吹雪机喷口是该持久生物圈的快照样本。2)一个显着的部分CO2固定在地下进行相关的arrhodatus Arcobacter sulfidicus通过还原TCA循环，这对初级生产的估计和解释的稳定碳同位素测量具有重要意义的aproteobacteria。3)形成硫的有机体产生独特的地球化学特征（生物标志物、同位素），这些特征被沉积下来，成为地质记录的一部分。该项目将涉及：在各种喷口生境使用新的无污染现场微生物取样装置进行取样;部署和回收装置，提供新的表面，以便对微生物的现场定植进行量化;船上培养，以评估功能;采用分子方法评估微生物群落与环境条件的关系;进行稳定同位素和放射性示踪剂研究，以查明自养型海底下微生物并测量其二氧化碳固定率;和脂质生物标志物研究，以提供该系统中微生物的多样性和相对丰度的独立评估。大量有机碳、特定脂类生物标志物和溶解无机碳的稳定同位素比率将提供关于特定类型喷口微生物所采用的固碳生理学和系统内碳转移的信息。该项目的更广泛影响包括在地球生物学领域的两个机构之间建立跨学科合作。预计结果将被整合到现有的课程和网页无论是在PI。s实验室或在各自的机构。该项目将支持在新兴的地球生物学领域培训一名研究生，并鼓励少数民族学生和女生参与这些工作。通过潜水和探索项目，PI还将针对中学生（6-8年级）和公众。将创建一个BIOLIPID网站，向研究人员和更广泛的社区传播这一项目和几个密切相关项目的结果。

The recent discovery of microbial populations beneath the deep ocean floor has far reaching implications in biology and has a potentially strong influence on a variety of biogeochemical processes. Hydrothermal fluid flowing through cracks and pores within the oceanic crust provides a potentially rich environment for subseafloor biological communities. Several recently published observations of .microbial eruptions point to the existence of a subseafloor biosphere that might contribute considerably to the productivity of these hydrothermal systems: Extensive discharges from so-called blizzard or snowblower vents (e.g., 9 deg N East pacific Rise) released large amounts of white flocculent material which accumulated into mats of 5 cm thickness. This material has since been identified as filamentous sulfur produced by novel microbes of the genus Arcobacter. The PIs plan an integrated microbiological and geochemical study of the abundance, distribution, and diversity of these filamentous-S producing microbes, and assessment of their ecological role at 9deg N EPR. Previous observations and the high likelihood for observing eruptive events with output of subsurface biomass mean that this site is well suited to address these questions. The proposed studies will test the following general hypotheses: 1) The prime habitat of filamentous-S-forming microbes is the shallow subsurface, i.e., that part of the subsurface characterized by the active mixing of hydrothermal fluid with seawater, and snowblower vents represent a snapshot sample of that persistent biosphere. 2) A significant portion of CO2-fixation in the subsurface is carried out by epsilon proteobacteria related to Candidatus Arcobacter sulfidicus by means of the reductive TCA cycle, which has significant implications for primary production estimates and interpretation of stable carbon isotope measurements. 3) The organisms forming filamentous-S produce a distinctive geochemical signature (biomarker, isotope) that is deposited and becomes part of the geological record. The project will involve: sampling at various vent habitats with a new device for uncontaminated in situ microbial sampling; deployment and recovery of devices to provide new surfaces for quantifying in situ colonization by microbes; shipboard culturing to assess function; molecular methods to assess the composition of the microbial community in relation to environmental conditions; stable isotope and radiotracer studies to identify autotrophic subseafloor microorganisms and measure their rates of CO2-fixation; and lipid biomarker studies to provide an independent assessment of the diversity and relative abundances of microbes in this system. Stable isotope ratios of bulk organic carbon, specific lipid biomarkers and dissolved inorganic carbon will provide information on the carbon-fixation physiologies employed by specific types of vent microbes and the transfer of carbon within the system. The broader impacts of this project include establishment of an inter-disciplinary collaboration between two institutions in the field of geobiology. It is expected that results will be integrated into coursework and web pages existing either in the PI.s labs or at the respective institutions. The project will support training of one graduate student in the emerging field of geobiology and encourage participation of minority and female students in these roles. Through the Dive and Discover project, the PIs will also target middle-school students (Grades 6-8) and the general public. A BIOLIPID website will be created to disseminate results on this and several closely related projects to researchers and the wider community.