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.

聚集体在海洋的有机物动力学中起着核心作用，具有各种微生物群落，可介导胶体，颗粒物和溶解有机物的转化和运输。由于这些聚集体可能是碳碳化力的热点，因此聚集体中的微生物动力学是强烈研究的重点。酶促活性的高率已经在聚集体中测量，但仅使用有限的底物代理来评估这些活动。然而，微生物细胞外酶的结构特异性至关重要，因为它们决定了可以由异养群落代谢的有机大分子的性质。在该项目中，北卡罗来纳大学教堂山分校的研究人员将使用浮游植物提取物，溶解的有机碳和多糖作为substrates AS substrates探测聚集物相关的微生物群落的酶促能力。将平行比较微生物群落的组成，以确定酶活性的差异是否与活性微生物群落的组成差异有关。由于有机骨料特别是作为下沉有机物的组成部分，在肾上非层中，或者从表面沉积物中重悬于通常包括具有相关有机物的矿物质颗粒，因此他们将研究与骨料相关的微生物社区水解表面相关的有机物的程度。初步研究进一步表明，特定酶被释放到水柱中，而其他酶仍与细胞和/或聚集体相关联，因此它们将测量无聚集样品中游离酶的活性以及游离酶的结构特异性。模型表明，当微生物获得合理的回报时，应主动释放游离酶。 研究人员将评估影响酶寿命的因素，即可用于测试有关微生物细胞外酶的模型预测的关键实验数据。更广泛的影响：该项目将有助于教学，两名大学生，一名研究生和一个博士后作为研究团队的组成部分。该项目的结果将在国家会议上介绍，并将在科学文献中发表。 该项目的结果将被纳入PI在研究生和本科级别教学的课程中。目前的两名本科研究助理是女性。