Collaborative Research: Marine priming effect - molecular mechanisms for the biomineralization of terrigenous dissolved organic matter in the ocean

合作研究：海洋启动效应——海洋中陆源溶解有机物生物矿化的分子机制

• 批准号: 1357242
• 负责人: Alison Buchan
• 金额: $ 46.3万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-01 至 2018-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1357242&HistoricalAwards=false
• 关键词: Collaborative; Research; Marine; priming; effect

Overview: Large fluxes of apparently refractory terrigenous dissolved organic matter (t-DOM) are transported through rivers to the coast each year, yet there are vanishingly low traces of t-DOM in the oceans. The removal of t-DOM is central to the global carbon cycle, yet the mechanisms that drive removal remain poorly understood. In soils, the presence of labile organic compounds is known to enhance the remineralization of recalcitrant compounds, a phenomenon known as the priming effect (PE). The PE is quantitatively important in soil systems, but has received little attention in aquatic systems despite its potential to explain C mineralization patterns at the land-sea interface. This project investigates the magnitude of PE in the coastal ocean and the metabolic and ecological mechanisms that give rise to it. It focuses on the microbial communities of US Atlantic Ocean coastal marshes. In these systems, river-borne t-DOM provides a particularly valuable and tractable model for evaluating the magnitude of the PE. The study utilizes a well-characterized DOM standard collected from a Georgia river as the model t-DOM material in a series of laboratory experiments with natural coastal microbial communities and cultures of heterotrophic marine bacteria of the Roseobacter lineage. Roseobacters are particularly appropriate biological models for this work as they are abundant in southeastern US coastal zones and are known to catabolize lignin and other plant-derived aromatic compounds. Long-term (60 day) incubation experiments will track the PE resulting from addition of labile DOM of differing chemical complexity. Changes in lignin phenols will be the primary measure of the influence of PE on t-DOM degradation, but the research also monitors a broader suite of aromatic compounds represented by optical properties and identified by high-resolution mass spectrometry. Measurements of the microbial response to added labile organic matter, via extracellular enzyme activities, bacterial production, community composition and gene transcript analysis, will reveal the biological mechanisms responsible for the PE. Experiments using Roseobacter strains will allow detailed investigation of the relationship between metabolic pathways, specific bacteria, and organic carbon mineralization in a well-defined experimental system. Data on gene expression, microbial activity, and DOM transformations from the lab experiments will be integrated to elucidate the specific metabolic pathways invoked as part of the PE and guide development of molecular tools to track genetic signatures along a river to coastal ocean transect in the final year of the project. Intellectual Merit: The role of heterotrophic microorganisms in remineralizing t-DOM at the land-sea interface is a central question in biological oceanography. Components of t-DOM, principally lignin, are refractory in the sense that degradation rates are typically slow relative to other biomolecules, and yet lignin is effectively removed somewhere between land and the open ocean. The project will determine whether priming plays a role in the rapid removal of t-DOM in the coastal ocean, provide evidence for the types of labile organic matter most effective as priming agents, and attemp to discover the metabolic pathways by which the PE is mediated. These studies have the potential to reveal conserved and predictable metabolic responses that may contribute to regulation of the transformation and turnover of naturally occurring semi-labile/refractory DOM in marine environments. As climate change is likely to affect fluxes of both terrigenous carbon and nutrients to the coastal ocean, understanding the magnitude and mechanisms of PE will be necessary to predict the geochemical consequences of these changing fluxes. Broader Impacts: The project will directly support the interdisciplinary and multi-institutional training of two graduate students and several undergraduate students. Training opportunities under a recently funded Research Experiences for Undergraduates (REU) program at UTK will be leveraged and extended to local UTK undergraduates participating in the project. Funding of this project will also provide support for research faculty to continue to develop an outreach program at a primarily minority high school in Newark NJ. Finally, all PIs will continue to disseminate their research results in presentations, papers and other forms on a timely basis.

概述：每年都有大量明显难降解的陆源溶解有机物（t-DOM）通过河流输送到海岸，但海洋中的t-DOM却很少。t-DOM的去除是全球碳循环的核心，但驱动去除的机制仍然知之甚少。在土壤中，已知不稳定有机化合物的存在会增强柠檬酸盐化合物的矿化作用，这种现象称为引发效应（PE）。在土壤系统中的PE是定量的重要，但在水生系统中很少受到关注，尽管它的潜力来解释C矿化模式在陆地-海洋界面。该项目调查了沿海海洋中PE的数量及其产生的代谢和生态机制。它关注美国大西洋沿海沼泽的微生物群落。在这些系统中，河流传播的t-DOM提供了一个特别有价值的和易处理的模型，用于评估的PE的大小。该研究利用了一个良好的特点DOM标准收集从格鲁吉亚河流作为模型的t-DOM材料在一系列的实验室实验中与自然的沿海微生物群落和培养的异养海洋细菌的Rosebellum血统。玫瑰杆菌是这项工作的特别合适的生物模型，因为它们在美国东南部沿海地区大量存在，并且已知分解代谢木质素和其他植物衍生的芳香族化合物。长期（60天）孵育实验将跟踪由添加不同化学复杂性的不稳定DOM产生的PE。木质素酚类的变化将是衡量PE对t-DOM降解影响的主要指标，但该研究还监测了以光学性质为代表并通过高分辨率质谱法鉴定的更广泛的芳香族化合物。通过胞外酶活性、细菌产量、群落组成和基因转录本分析，测量微生物对添加的不稳定有机物的反应，将揭示PE的生物学机制。使用Roseplastics菌株的实验将允许在定义明确的实验系统中详细研究代谢途径，特定细菌和有机碳矿化之间的关系。从实验室实验的基因表达，微生物活性和DOM转换的数据将被整合，以阐明特定的代谢途径调用作为PE的一部分，并指导分子工具的开发，以跟踪遗传签名沿着河流到沿海海洋样带在项目的最后一年。智力优势：异养微生物在陆地-海洋界面t-DOM分解中的作用是生物海洋学的核心问题。t-DOM的成分，主要是木质素，是难降解的，因为降解速率通常相对于其他生物分子缓慢，但木质素在陆地和公海之间的某个地方被有效地去除。该项目将确定启动是否在沿海海洋中快速去除t-DOM中发挥作用，为最有效的启动剂不稳定有机物的类型提供证据，并探索发现PE介导的代谢途径。这些研究有可能揭示保守和可预测的代谢反应，可能有助于调节自然发生的半不稳定/难降解DOM在海洋环境中的转化和营业额。由于气候变化可能会影响陆源碳和营养盐的通量到沿海海洋，了解PE的规模和机制将是必要的，以预测这些变化通量的地球化学后果。更广泛的影响：该项目将直接支持两名研究生和几名本科生的跨学科和多机构培训。根据最近资助的研究经验本科生（REU）计划在UTK的培训机会将被利用，并扩展到当地的UTK本科生参与该项目。该项目的资金还将为研究人员提供支持，以继续在新泽西州纽瓦克的一所主要为少数民族的高中开展外展计划。最后，所有专业研究机构将继续及时以演讲、论文和其他形式传播其研究成果。