Understanding microbial control of dissolved organic nitrogen (DON) in the ocean: New amino acid tracers for bacterial source and cycling of refractory DON

了解海洋中溶解有机氮 (DON) 的微生物控制：用于细菌来源和难治性 DON 循环的新型氨基酸示踪剂

• 批准号: 2124180
• 负责人: Matthew McCarthy
• 金额: $ 84.97万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2124180&HistoricalAwards=false
• 关键词: Understanding; microbial; control; dissolved; organic

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).One of the most mysterious components of the global nitrogen cycle is the vast amount of dissolved nitrogen-containing organic molecules (dissolved organic nitrogen, or “DON”) which exist in the ocean. The identities of these molecules are mostly unknown, but they are important in the ocean’s biological and geochemical cycles, because they persist for many thousands of years and in many cases these molecules are too complex for simple organisms at the base of the food web to use. This project will develop new chemical tools to understand this material, including stable isotopes, radioisotopes, and the chirality of amino acids. Together, this new set of tracers will focus on the roles of marine bacteria as sources and creators of persistent dissolved organic nitrogen. The project will begin in the laboratory, where the team will first grow large cultures of ocean algae. Natural ocean bacteria will then be added, and investigators will measure the proposed new tracers in dissolved nitrogen materials created. These data will reveal how the proposed tracers work: how and when they are produced, if they map to bacterial sources, and how bacterial degradation may affect them. The investigators will then conduct a series of field expeditions at contrasting sites on the California coast and in the central Pacific Ocean, isolating large amounts of natural dissolved organic nitrogen. The team will apply what has been learned in the lab together with the first ever radiocarbon measurements on individual tracer molecules. Together these activities will open a new window into sources and cycling of the critical marine dissolved organic nitrogen material. The project will support the education, training, and career development of a graduate student, a postdoctoral researcher, and undergraduate students from underrepresented groups, who will be recruited to receive real hands-on laboratory and field experience. This project will develop three new amino acid–based proxies for bacterial source and alteration of dissolved organic nitrogen: 1) compound-specific stable carbon isotope fingerprinting of essential amino acids, 2) a recently discovered suite of new D-amino acids found to be concentrated in radiocarbon-old, low molecular weight DON material, and 3) individual amino acid radiocarbon values for key hypothesized tracer amino acids. The investigators hypothesize that refractory ocean DON is essentially completely microbial, however that it is also far more diverse than has previously been understood in terms of its sources, molecular composition, and especially cycling rates. In particular, the project will test the idea of completely different DON origin, molecular composition, and cycling rates in high vs. low molecular weight DON fractions throughout the water column. Autotrophic and heterotrophic bacterial growth / degradation experiments will test assumptions about the sources and degradation- related changes to D/L and stable carbon isotope signatures. Synoptically making these measurements together with individual amino acid radiocarbon values in high productivity coastal vs. oligotrophic Pacific gyre DON in both surface and deep ocean will allow understanding the diversity of DON bacterial sources, degradation impacts, and N-specific cycling rates for the first time.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该奖项的全部或部分资金根据《2021 年美国救援计划法案》（公法 117-2）提供。 全球氮循环中最神秘的组成部分之一是海洋中存在的大量溶解的含氮有机分子（溶解有机氮，或“DON”）。这些分子的身份大多未知，但它们在海洋的生物和地球化学循环中很重要，因为它们持续了数千年，而且在许多情况下，这些分子对于食物网底部的简单生物体来说太复杂而无法使用。该项目将开发新的化学工具来了解这种材料，包括稳定同位素、放射性同位素和氨基酸的手性。这套新的示踪剂将共同关注海洋细菌作为持久溶解有机氮的来源和创造者的作用。该项目将从实验室开始，团队将首先在那里培养大量的海洋藻类。然后将添加天然海洋细菌，研究人员将测量所产生的溶解氮材料中拟议的新示踪剂。这些数据将揭示所提出的示踪剂是如何工作的：它们是如何以及何时产生的，它们是否映射到细菌来源，以及细菌降解如何影响它们。研究人员随后将在加利福尼亚海岸和太平洋中部的不同地点进行一系列实地考察，分离大量天然溶解的有机氮。该团队将应用在实验室中学到的知识以及对单个示踪分子的首次放射性碳测量。这些活动将为了解关键海洋溶解有机氮物质的来源和循环打开一扇新窗口。该项目将支持来自弱势群体的研究生、博士后研究员和本科生的教育、培训和职业发展，他们将被招募以获得真正的实验室实践和现场经验。该项目将开发三种基于氨基酸的新代理，用于细菌来源和溶解有机氮的改变：1）必需氨基酸的化合物特异性稳定碳同位素指纹图谱，2）最近发现的一组新的 D-氨基酸，被发现集中在放射性碳旧的低分子量 DON 材料中，以及 3）关键假设的单个氨基酸放射性碳值 示踪氨基酸。研究人员假设，难降解的海洋 DON 本质上完全是微生物，但它在来源、分子组成，尤其是循环速率方面也比以前所理解的要多样化得多。特别是，该项目将测试整个水柱中高分子量 DON 组分与低分子量 DON 组分完全不同的 DON 来源、分子组成和循环速率的想法。自养和异养细菌生长/降解实验将测试有关 D/L 和稳定碳同位素特征的来源和降解相关变化的假设。从总体上来说，将这些测量与表层和深海中高产沿海 DON 与寡营养太平洋环流 DON 中的单个氨基酸放射性碳值一起进行，将有助于我们首次了解 DON 细菌来源的多样性、降解影响和 N 特异性循环率。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力和知识进行评估，被认为值得支持。 更广泛的影响审查标准。