Extracellular enzymes in aggregates and contributions of free enzymes to hydrolytic activities: Consequences for organic mater remineralizations in marine systems

聚集体中的细胞外酶和游离酶对水解活性的贡献：海洋系统中有机物再矿化的后果

• 批准号: 0848703
• 负责人: Carol Arnosti
• 金额: $ 57.1万
• 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: 2009
• 资助国家: 美国
• 起止时间: 2009-03-15 至 2013-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0848703&HistoricalAwards=false
• 关键词: Extracellular; enzymes; aggregates; contributions; free

Aggregates play a central role in organic matter dynamics in the ocean, harboring diverse communities of microorganisms that mediate the transformations and transport of colloidal, particulate, and dissolved organic matter. Because these aggregates can be hot spots of carbon remineralization, microbial dynamics in aggregates have been a focus of intense investigation. High rates of enzymatic activities have been measured in aggregates, but only a limited range of substrate proxies have been used to assess these activities. The structural specificities of microbial extracellular enzymes are critical, however, since they determine the nature of organic macromolecules that can be metabolized by heterotrophic communities. In this project, investigators at the University of North Carolina at Chapel Hill will probe the enzymatic capabilities of aggregate-associated microbial communities and compare them with non-aggregate associated communities using phytoplankton extracts, dissolved organic carbon, and polysaccharides as substrates. The composition of the microbial communities will be compared in parallel to determine whether differences in the spectrum of enzyme activities are related to compositional differences in the active microbial communities. Since organic aggregates particularly as components of sinking organic matter, in the nepheloid layer, or resuspended from surface sediments often include mineral particles with associated organic matter, they will investigate the extent to which surface-associated organic matter can be hydrolyzed by aggregate-associated microbial communities. Preliminary investigations further suggest that specific enzymes are released into the water column while other enzymes remain associated with cells and/or aggregates, so they will measure the activities as well as the structural specificities of free enzymes in aggregate-free samples. Models suggest that active release of free enzymes should occur when microorganisms receive a reasonable return. The investigators will assess factors affecting enzyme lifetimes, critical experimental data that could be used to test conflicting model predictions about microbial extracellular enzymes. Broader Impacts: This project will contribute to teaching and learning, with two undergraduates, a graduate student, and a postdoc as integral members of the research team. Results of the project will be presented at national meetings and will be published in the scientific literature. Results of this project will be incorporated into classes the PI teaches at both graduate and undergraduate levels. Two of the current undergraduate research assistants are women.

聚集体在海洋中的有机物动力学中起着核心作用，包含介导胶体，颗粒和溶解有机物的转化和运输的微生物的多样性社区。由于这些聚集体可能是碳矿化的热点，聚集体中的微生物动力学一直是研究的焦点。高速率的酶活性已被测量的聚集体，但只有有限范围的底物代理已被用于评估这些活动。然而，微生物胞外酶的结构特异性是至关重要的，因为它们决定了可以被异养群落代谢的有机大分子的性质。在这个项目中，查佩尔山的北卡罗来纳州大学的研究人员将利用浮游植物提取物、溶解有机碳和多糖作为底物，探测聚集体相关微生物群落的酶促能力，并将其与非聚集体相关群落进行比较。将平行比较微生物群落的组成，以确定酶活性谱的差异是否与活性微生物群落的组成差异有关。由于有机聚集体，特别是作为下沉有机物的组成部分，在雾状层中，或从表面沉积物中重新悬浮，通常包括矿物颗粒与相关的有机物，他们将调查在何种程度上表面相关的有机物可以水解聚集体相关的微生物群落。初步研究进一步表明，特定的酶被释放到水柱中，而其他酶仍然与细胞和/或聚集体相关联，因此它们将测量无聚集体样品中游离酶的活性和结构特异性。模型表明，当微生物获得合理的回报时，游离酶的主动释放应该发生。 研究人员将评估影响酶寿命的因素，这些关键实验数据可用于测试有关微生物胞外酶的相互矛盾的模型预测。更广泛的影响：这个项目将有助于教学和学习，两个本科生，一个研究生和一个博士后作为研究团队的组成成员。该项目的成果将在国家会议上介绍，并将在科学文献中发表。 这个项目的结果将被纳入类PI教在研究生和本科生水平。目前有两名本科生研究助理是妇女。