Microbial processes of pelagic anaerobic methane cycling in oxygen minimum zones

最低氧区中上层厌氧甲烷循环的微生物过程

• 批准号: 1558916
• 负责人: Frank Stewart
• 金额: $ 57.15万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558916&HistoricalAwards=false
• 关键词: Microbial; processes; pelagic; anaerobic; methane

The overarching goal of this research is to understand how bacteria in marine oxygen minimum zones (OMZs) control interactions between the ocean methane and nitrogen cycles. OMZs constitute the largest pool of methane in the ocean water column, and also serve as sites where anaerobic microbes convert the essential element nitrogen from a form that can be used by organisms to a gaseous form (N2) that can be lost from the ocean. Recent studies, predominantly in freshwater environments, have discovered novel bacteria that link methane consumption to pathways of nitrogen loss. These researchers have recently shown that such bacteria also occur in OMZs. However, the contributions of these bacteria to ocean methane and nitrogen flux remain unknown. Here, the researchers will use a combination of genomics and biochemical measurements to characterize the metabolic potential and diversity of these bacteria in OMZs and to quantify their contribution to methane and nitrogen transformations. Meeting this goal is critical for constraining bulk fluxes of these chemicals in the open ocean and for predictive models of climate change, notably given the importance of methane as a potent greenhouse gas and the prediction that OMZs will expand with global warming. This project is also committed to enhancing knowledge of marine microbiology in the public arena and educational communities. The investigators will incorporate results and concepts from this research into instructional modules for use in the Summer Workshop in Marine Science (SWiMS) at Georgia Tech (https://swimsgatech.wordpress.com/), an annual workshop to train middle and high school educators in marine science using lectures and lab exercises. This project will also involve training of undergraduate students, a postdoc, and local high school teachers through the Georgia Tech GIFT Program. Through the combined research and educational activities, this research will determine how low-oxygen conditions in the ocean regulate pelagic microbial diversity and methane cycling, as well as inform, engage, and excite scientific and general audiences about marine microbiology and biogeochemistry. This research focuses specifically on bacteria conducting nitrite-dependent anaerobic methane oxidation (n-damo). This process has been described in bacteria of the NC10 division, in which a dismutation reaction generates both N2 and O2 gas, with the O2 used for intra-aerobic methane oxidation. Although NC10 bacteria have been described primarily from nitrite-rich freshwater and marine sediments, recent evidence indicates that NC10 are also present in anoxic OMZs. Given that OMZs contain substantial pools of the n-damo substrates nitrite and methane, it is hypothesized that OMZs harbor an anaerobic methane cycle coupled to nitrogen loss, and that this coupling is mediated by n-damo NC10 bacteria that occur as ubiquitous components in diverse OMZs. To test this hypothesis, the researchers will 1) quantify the contribution of n-damo to OMZ methane oxidation, N2 production, and oxygen production rates, 2) characterize the diversity and ecophysiology of OMZ NC10 isolates through enrichments and single-cell genomics, and 3) survey the abundance, diversity, and activity of NC10 bacteria across distinct OMZ systems.

这项研究的首要目标是了解海洋最低含氧区(OMZ)中的细菌如何控制海洋甲烷和氮循环之间的相互作用。OMZ构成了海洋水柱中最大的甲烷池，也是厌氧微生物将必要的元素氮从生物体可以利用的形式转化为可能从海洋中失去的气体形式(N2)的场所。最近的研究，主要是在淡水环境中，发现了将甲烷消耗与氮损失途径联系起来的新型细菌。这些研究人员最近表明，这种细菌也出现在OMZ中。然而，这些细菌对海洋甲烷和氮通量的贡献仍不清楚。在这里，研究人员将使用基因组学和生化测量相结合的方法来表征这些细菌在OMZ中的代谢潜力和多样性，并量化它们对甲烷和氮转化的贡献。实现这一目标对于限制这些化学品在公海中的大量通量和气候变化的预测模型至关重要，特别是考虑到甲烷作为一种强有力的温室气体的重要性，以及预测OMZ将随着全球变暖而扩大。该项目还致力于在公共领域和教育界加强海洋微生物学知识。研究人员将把这项研究的结果和概念纳入教学模块，用于佐治亚理工学院的海洋科学夏季研讨会(https://swimsgatech.wordpress.com/)，)，这是一个一年一度的研讨会，通过讲座和实验室练习培训初中和高中的海洋科学教育工作者。该项目还将通过佐治亚理工学院礼物计划对本科生、博士后和当地高中教师进行培训。通过研究和教育相结合的活动，这项研究将确定海洋低氧条件如何调节远洋微生物多样性和甲烷循环，以及向科学和普通受众提供关于海洋微生物学和生物地球化学的信息、参与和激发他们的兴趣。本研究的重点是进行依赖亚硝酸盐的厌氧甲烷氧化的细菌(n-达摩)。这个过程已经在NC10部门的细菌中描述过，在这个过程中，置换反应同时产生氮气和氧气气体，氧气用于好氧内甲烷氧化。尽管NC10细菌主要来自富含亚硝酸盐的淡水和海洋沉积物，但最近的证据表明，NC10也存在于缺氧的OMZ中。鉴于OMZ含有大量的n-达摩底物亚硝酸盐和甲烷，推测OMZ存在一个与氮损失耦合的厌氧甲烷循环，这种耦合是由n-达摩NC10细菌介导的，这些细菌在不同的OMZ中作为普遍存在的成分出现。为了验证这一假设，研究人员将1)量化n-达摩对OMZ甲烷氧化、氮气产生和氧气产生速率的贡献，2)通过增菌和单细胞基因组学表征OMZ NC10菌株的多样性和生态生理学，3)调查不同OMZ系统中NC10细菌的丰度、多样性和活性。