A mechanistic microbial underpinning for the size-reactivity continuum of dissolved organic carbon degradation

溶解有机碳降解的尺寸反应连续体的微生物机制基础

• 批准号: 1736772
• 负责人: Carol Arnosti
• 金额: $ 59.84万
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736772&HistoricalAwards=false
• 关键词: mechanistic; microbial; underpinning; size; reactivity

Marine dissolved organic matter (DOM) is one of the largest actively-cycling reservoirs of organic carbon on the planet, and thus a major component of the global carbon cycle. The high molecular weight (HMW) fraction of DOM is younger in age and more readily consumed by microbes than lower molecular weight (LMW) fractions of DOM, but the reasons for this difference in reactivity between HMW DOM and LMW DOM are unknown. Two factors may account for the greater reactivity of HMW DOM: (i) targeted uptake of HMW DOM by specific bacteria, a process the PI and her collaborators at the Max Planck Institute for Marine Microbiology (MPI) recently identified in surface ocean waters; and (ii) a greater tendency of HMW DOM to aggregate and form gels and particles, which can be colonized by bacteria that are well-equipped to breakdown organic matter. Scientists and students from the University of North Carolina (UNC) - Chapel Hill will collaborate with researchers at the MPI for Marine Microbiology (Bremen, Germany) to investigate this breakdown of HMW DOM by marine microbial communities. These investigations will include a field expedition in the North Atlantic, during which HMW DOM degradation rates and patterns will be compared in different water masses and under differing conditions of organic matter availability. DOM aggregation potential, and degradation rates of these aggregates, will also be assessed. Specialized microscopy will be used in order to pinpoint HMW DOM uptake mechanisms and rates. The work will be complemented by ongoing studies of specific bacteria that breakdown HMW DOM, their genes, and their proteins. Graduate as well as undergraduate students will participate as integral members of the research team in all aspects of the laboratory and field work; aspects of the project will also be integrated into classes the scientist teaches at UNC. The existence of a size-reactivity continuum of DOM - observations and measurements showing that HMW DOM tends to be younger and more reactive than lower MW DOM ? has been demonstrated in laboratory and field investigations in different parts of the ocean. A mechanistic explanation for the greater reactivity of HMW DOM has been lacking, however. This project will investigate the mechanisms and measure rates of HMW DOM degradation, focusing on identifying the actors and determining the factors that contribute to rapid cycling of HMW DOM. Collaborative work at UNC and MPI-Bremen recently identified a new mechanism of HMW substrate uptake common among pelagic marine bacteria: these bacteria rapidly bind, partially hydrolyze, and transport directly across the outer membrane large fragments of HMW substrates that can then be degraded within the periplasmic space, avoiding production of LMW DOM in the external environment. This mode of substrate processing has been termed selfish, since targeted HMW substrate uptake sequesters resources away from other members of microbial communities. Measurements and models thus must account for three modes of substrate utilization in the ocean: selfish, sharing (external hydrolysis, leading to low molecular weight products), and scavenging (uptake of low molecular weight hydrolysis products without production of extracellular enzymes). Using field studies as well as mesocosm experiments, the research team will investigate the circumstances and locations at which different modes of substrate uptake predominate. A second focal point of the project is to determine the aggregation potential and microbial degradation of aggregated HMW DOM. Preliminary studies have demonstrated that particle-associated microbial communities utilize a broader range of enzymatic capabilities than their free-living counterparts. These capabilities equip particle-associated communities to effectively target a broad range of complex substrates. The project will thus focus on two key aspects of HMW DOM - the abilities of specialized bacteria to selectively sequester HMW substrates, as well as the greater potential of HMW substrates to aggregate ? and will quantify these factors at different locations and depths in the ocean. The project will thereby provide a mechanistic underpinning for observations of the DOC size-reactivity continuum, an essential part of developing an overall mechanistic understanding of organic matter degradation in the ocean.

海洋溶解有机物（DOM）是地球上有机碳的最大的活跃循环储层之一，因此是全球碳循环的主要组成部分。 DOM的高分子量（HMW）的年龄年龄更年轻，而被微生物的消耗量比DOM的低分子量（LMW）分数更容易消耗，但是HMW DOM和LMW DOM之间反应性差异的原因尚不清楚。有两个因素可以解释HMW DOM的反应性更大：（i）特定细菌对HMW DOM的靶向吸收，这是Max Planck海洋微生物学研究所（MPI）的PI及其合作者最近在地表海水中发现的。 （ii）HMW DOM更倾向于聚集并形成凝胶和颗粒，这些凝胶和颗粒可以被细菌殖民，这些细菌均具有良好的分解有机物。北卡罗来纳大学（UNC） - 教堂山的科学家和学生将与MPI的海洋微生物学（德国布雷门岛）的研究人员合作研究海洋微生物社区对HMW DOM的这种细分。这些调查将包括在北大西洋的一次实地考察，在此期间，将在不同的水质量和有机物可用性的不同条件下比较HMW DOM降解率和模式。这些聚集体的DOM聚集潜力和降解率也将被评估。将使用专门的显微镜来查明HMW DOM吸收机制和速率。持续的对特定细菌的研究将互补，这些细菌损坏了HMW DOM，其基因和蛋白质。毕业生以及本科生将在实验室和现场工作的各个方面担任研究团队的组成部分；该项目的各个方面还将集成到科学家在UNC上教授的课程。 DOM观测和测量值的大小反应连续性的存在表明HMW DOM往往比低MW DOM更年轻，更具反应性？在海洋不同地区的实验室和现场调查中已证明。但是，缺乏对HMW DOM反应性更大的机械解释。该项目将研究HMW DOM降解的机制和测量率，重点是识别参与者并确定有助于HMW DOM快速循环的因素。 UNC和MPI-BREMEN的合作工作最近确定了上层海洋细菌中常见的HMW底物摄取的新机制：这些细菌迅速结合，部分水解，并直接在HMW底物的外膜大型碎片上运输，可以在外部空间内降级，避免使用LMMW的环境，从而在周围的生产中脱脂。这种底物处理模式已被称为自私，因为针对的HMW基板吸收吸收隔离的资源远离微生物群落的其他成员。因此，测量和模型必须考虑海洋中底物利用的三种模式：自私，共享（外部水解，导致低分子量产物产物）和清除（对低分子量水解产物的吸收而不产生细胞外酶）。使用现场研究以及中验实验，研究团队将调查不同底物摄取模式占主导地位的情况和位置。该项目的第二个焦点是确定聚集的HMW DOM的聚合潜力和微生物降解。初步研究表明，粒子相关的微生物群落比其自由生活的酶能力更广泛。这些功能能够使粒子相关群落有效地瞄准广泛的复杂底物。因此，该项目将集中在HMW DOM的两个关键方面 - 专门细菌有选择性隔离HMW底物的能力，以及HMW底物对聚集体的较大潜力？并将在海洋中的不同位置和深度量化这些因素。因此，该项目将为观察DOC尺寸 - 反应连续体的观察提供一个机械基础，这是对海洋中有机物降解的整体机械理解的重要组成部分。

项目成果

Community structural differences shape microbial responses to high molecular weight organic matter

• DOI: 10.1111/1462-2920.14485
• 发表时间: 2019-02-01
• 期刊: ENVIRONMENTAL MICROBIOLOGY
• 影响因子: 5.1
• 作者: Balmonte, John Paul;Buckley, Andrew;Arnosti, Carol
• 通讯作者: Arnosti, Carol

Single cell fluorescence imaging of glycan uptake by intestinal bacteria

• DOI: 10.1038/s41396-019-0406-z
• 发表时间: 2019-07-01
• 期刊: ISME JOURNAL
• 影响因子: 11
• 作者: Hehemann, Jan-Hendrik;Reintjes, Greta;Abbott, D. Wade
• 通讯作者: Abbott, D. Wade

Global ecotypes in the ubiquitous marine clade SAR86

• DOI: 10.1038/s41396-019-0516-7
• 发表时间: 2020-01-01
• 期刊: ISME JOURNAL
• 影响因子: 11
• 作者: Hoarfrost, Adrienne;Nayfach, Stephen;Pollard, Katherine S.
• 通讯作者: Pollard, Katherine S.

The Enduring Questions: What's for Dinner? Where's My Knife? …and Can I Use My Fingers? (Unanswered) Questions Related to Organic Matter and Microbes in Marine Sediments

• DOI: 10.3389/fmars.2019.00629
• 发表时间: 2019-10
• 期刊: Frontiers in Marine Science
• 影响因子: 3.7
• 作者: C. Arnosti;K. Hinrichs;S. Coffinet;H. Wilkes;S. Pantoja

Gulf Stream Ring Water Intrusion on the Mid-Atlantic Bight Continental Shelf Break Affects Microbially Driven Carbon Cycling

• DOI: 10.3389/fmars.2019.00394
• 发表时间: 2019-07
• 期刊: Frontiers in Marine Science
• 影响因子: 3.7
• 作者: A. Hoarfrost;J. Balmonte;S. Ghobrial;Kai Ziervogel;J. Bane;G. Gawarkiewicz;C. Arnosti