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）是地球上最大的有机碳活性循环库之一，因此是全球碳循环的主要组成部分。高分子量（HMW）部分的DOM是年轻的年龄和更容易被微生物消耗比低分子量（LMW）部分的DOM，但这种差异的原因高分子量DOM和低分子量DOM之间的反应性是未知的。两个因素可能是高分子量DOM反应性更强的原因：（i）特定细菌对高分子量DOM的靶向吸收，这是马克斯普朗克海洋微生物学研究所（MPI）的PI及其合作者最近在海洋表面沃茨中发现的一个过程;（ii）高分子量DOM更倾向于聚集并形成凝胶和颗粒，这些颗粒可以被装备精良的细菌定殖，以分解有机物质。来自北卡罗来纳州大学（北卡罗来纳）-查佩尔山的科学家和学生将与MPI海洋微生物学（不莱梅，德国）的研究人员合作，调查海洋微生物群落对HMW DOM的分解。这些调查将包括在北大西洋的实地考察，在此期间，高分子量DOM降解率和模式将在不同的水团和不同的条件下的有机物质的可用性进行比较。还将评估DOM聚集潜力和这些聚集体的降解速率。将使用专门的显微镜，以查明高分子量DOM吸收机制和速率。这项工作将通过正在进行的对分解HMW DOM的特定细菌，其基因和蛋白质的研究来补充。研究生和本科生将作为研究团队的组成成员参与实验室和实地工作的各个方面;该项目的各个方面也将融入科学家在斯坦福大学教授的课程中。存在的DOM的大小反应连续-观测和测量表明，高分子量DOM往往是年轻的，更活跃的低分子量DOM？已在海洋不同区域的实验室和实地调查中得到证实。然而，对HMW DOM的更大反应性的机械解释一直缺乏。本项目将研究高分子量DOM降解的机制和测量速率，重点是识别参与者并确定有助于高分子量DOM快速循环的因素。最近，在海洋微生物研究所和MPI Bremen的合作工作中发现了一种在远洋海洋细菌中常见的HMW底物摄取的新机制：这些细菌快速结合，部分水解，并直接穿过外膜运输HMW底物的大片段，然后可以在周质空间内降解，避免在外部环境中产生LMW DOM。这种底物处理模式被称为自私的，因为有针对性的高分子量底物摄取隔离资源远离其他成员的微生物群落。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）和清除（吸收低分子量水解产物而不产生胞外酶）。通过实地研究和围隔实验，研究小组将调查不同基质吸收模式占主导地位的环境和位置。该项目的第二个重点是确定聚集的高分子量DOM的聚集潜力和微生物降解。初步研究表明，与颗粒相关的微生物群落比自由生活的微生物群落利用更广泛的酶促能力。这些能力使颗粒相关的社区能够有效地针对广泛的复杂基质。因此，该项目将集中在高分子量DOM的两个关键方面-专门的细菌选择性螯合高分子量底物的能力，以及高分子量底物聚集的更大潜力？并将在海洋的不同位置和深度量化这些因素。因此，该项目将提供一个机制的DOC的大小反应连续观测的基础上，一个重要的组成部分，发展一个整体的机械理解的有机物在海洋中的降解。

项目成果

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

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

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

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.

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