Collaborative Research: Quantifying N2 fixation rates of noncyanobacterial diazotrophs and environmental controls on their activity

合作研究：量化非蓝藻固氮菌的 N2 固定率及其活性的环境控制

• 批准号: 2023498
• 负责人: Kendra Turk-Kubo
• 金额: $ 54.35万
• 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: 2021-04-01 至 2025-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2023498&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantifying; N2; fixation

Nitrogen (N) is an important element in the ocean that limits the growth of the microscopic marine plants, phytoplankton. Estimates suggest N inputs and losses may not be balanced in the modern ocean, and thus an underestimation of N inputs may explain this imbalance. The conversion of gaseous N2 to biologically available N (N2 fixation) is the largest source of new N to the ocean. It is possible that the “missing” N can be explained by identifying new sources of N2 fixation. N2 fixation relies on a group of microorganisms, termed “diazotrophs,” that utilize N2 for growth, unlike other marine microorganisms. Diazotrophs fall into two groups, cyanobacterial diazotrophs, which are able to derive energy through photosynthesis, and non-cyanobacterial diazotrophs (NCDs), which require a non-light-based energy source. Next to nothing is known about the ecology and biology of NCDs, except that they are ubiquitous in the ocean and contain the nitrogen fixing gene, but no direct measurements of their N2 fixation activity exist. Recent molecular advances for studying organisms at the single cell level now makes the measurement of N2 fixation by NCDs possible. This study is focused on determining whether marine NCDs are actually fixing N2 in the environment and understanding how their N2 fixation is modulated. Determining if NCD activity is an important missing N source in the global oceans has the potential to fill a critical gap in our understanding of the marine N cycle. This project supports early career STEM researchers including a graduate student and a postdoctoral scientist, as well as undergraduate students through several programs including UCSC’s California Alliance for Minority Participation (CAMP).Nitrogen fixation, the microbial process of converting N2 into biologically available ammonia, is an important source of N in the oceans. Historically, research has focused on the most conspicuous diazotrophs, such as Trichodesmium, but the discovery of unicellular cyanobacterial and non-cyanobacterial diazotrophs (NCDs) in the open ocean revealed a broader diversity than previously thought. Much of what is known about NCDs is restricted to presence, abundance estimates and transcriptional activity from gene surveys. NCDs are globally distributed throughout coastal and oligotrophic environments, however, it is not known whether NCDs supply N to support primary productivity. Measurements of marine NCDs are needed to determine if NCDs are actively fixing N2. This study is focused on measuring single cell NCD N2 fixation rates from a variety of taxa living in well-lit, oxygen-rich coastal and oligotrophic surface waters in the North Pacific and Arctic Oceans. The investigators are using a cultivation-independent technique called geneFISH to microscopically visualize and localize NCDs and measuring the incorporation of 15N2 into single cells using nanoscale secondary ion mass spectrometry. Beyond measuring in situ NCD N2 fixation rates, experiments are being conducted to determine environmental controls on single cell NCD N2 fixation (light, temperature, dissolved organic matter, dissolved inorganic N, and iron). Obtaining single cell NCD N2 fixation rates from a range of taxa, under different experimental conditions and in coastal and oligotrophic environments will provide information to link their presence to N2 fixation activity, determine the quantitative significance of NCDs in the marine environment, and set the stage for their inclusion in biogeochemical models.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.

氮 (N) 是海洋中限制微观海洋植物、浮游植物生长的重要元素。估计表明现代海洋中氮的输入和损失可能不平衡，因此低估氮输入可能解释了这种不平衡。气态 N2 转化为生物可用 N（N2 固定）是海洋新 N2 的最大来源。“缺失”的 N 可能可以通过识别 N2 固定的新来源来解释。氮气固定依赖于一组称为“固氮微生物”的微生物，与其他海洋微生物不同，固氮微生物分为两类：蓝藻固氮微生物，能够通过光合作用获取能量，以及非蓝藻固氮微生物 (NCD)。 ），这需要非光能源，人们对非传染性疾病的生态学和生物学几乎一无所知，只不过它们在海洋中普遍存在并且含有固氮基因，但目前尚无直接测量其固氮活性的方法，目前在单细胞水平上研究生物体的分子进展使得通过非传染性疾病来测量固氮活性成为可能。重点是确定海洋非传染性疾病是否确实在环境中固定氮，并了解它们的氮固定是如何调节的，确定非传染性疾病活动是否是全球海洋中重要的缺失氮源，有可能填补一个关键空白。该项目支持早期职业 STEM 研究人员，包括一名研究生和一名博士后科学家，以及通过 UCSC 加州少数族裔参与联盟 (CAMP) 等项目的本科生。固氮，微生物过程。将 N2 转化为生物可利用的氨的过程是海洋中 N 的重要来源。历史上，研究主要集中在最引人注目的固氮微生物上，例如 Trichodesmium。在公海中发现的单细胞蓝藻和非蓝藻固氮菌 (NCD) 揭示了比之前想象的更广泛的多样性。对 NCD 的了解主要在于其存在、丰度估计有限以及 NCD 的转录活性分布在全球范围内。然而，在整个沿海和贫营养环境中，尚不清楚非传染性疾病是否提供氮来支持初级生产力，需要对海洋非传染性疾病进行测量以确定非传染性疾病是否正在积极修复。 N2。这项研究的重点是测量生活在北太平洋和北冰洋光线充足、富氧的沿海和贫营养表层水中的各种类群的单细胞 NCD N2 固定率。研究人员正在使用一种独立于培养的技术。称为geneFISH的技术可在显微镜下可视化和定位NCD，并使用纳米级二次离子质谱法测量15N2融入单细胞的情况，除了测量原位NCD N2固定率外，还进行了实验以确定环境。对单细胞 NCD N2 固定的控制（光、温度、溶解的有机物、溶解的无机氮和铁）在不同的实验条件下以及沿海和寡营养环境中从一系列分类单元获得单细胞 NCD N2 固定率将提供信息。将其存在与 N2 固定活动联系起来，确定非传染性疾病在海洋环境中的定量重要性，并为将其纳入生物地球化学模型奠定基础。该奖项反映了 NSF 的法定使命，并被认为值得通过以下方式获得支持：使用基金会的智力价值和更广泛的影响审查标准进行评估。

项目成果

Seasonal and spatial patterns in diazotroph community composition at Station ALOHA

ALOHA 站固氮微生物群落组成的季节和空间格局

• DOI: 10.3389/fmars.2023.1130158
• 发表时间: 2023-05
• 期刊: Frontiers in Marine Science
• 影响因子: 3.7
• 作者: Turk;Henke, Britt A.;Gradoville, Mary R.;Magasin, Jonathan D.;Church, Matthew J.;Zehr, Jonathan P.
• 通讯作者: Zehr, Jonathan P.

Cell-specific measurements show nitrogen fixation by particle-attached putative non-cyanobacterial diazotrophs in the North Pacific Subtropical Gyre

细胞特异性测量显示北太平洋副热带环流中颗粒附着的推定非蓝藻固氮菌的固氮作用

• DOI: 10.1038/s41467-022-34585-y
• 发表时间: 2022-11-15
• 期刊: Nature Communications
• 影响因子: 16.6
• 作者: Harding, Katie J.;Turk-Kubo, Kendra A.;Mak, Esther Wing Kwan;Weber, Peter K.;Mayali, Xavier;Zehr, Jonathan P.
• 通讯作者: Zehr, Jonathan P.

Composition and distribution of diazotrophs in the Baltic Sea

波罗的海固氮生物的组成和分布

• DOI: 10.1016/j.ecss.2023.108527
• 发表时间: 2023-10-01
• 期刊: Estuarine, Coastal and Shelf Science
• 作者: Ellen R. Salamon Slater;K. Turk;Søren Hallstrøm;K. Kesy;P. Laas;Jonathan D. Magasin;J. Zehr;Matthias Labrenz;L. Riemann
• 通讯作者: L. Riemann

Non-cyanobacterial diazotrophs: global diversity, distribution, ecophysiology, and activity in marine waters

非蓝藻固氮菌：全球多样性、分布、生态生理学和海水活动

• DOI: 10.1093/femsre/fuac046
• 发表时间: 2023-11-01
• 期刊: FEMS Microbiology Reviews
• 影响因子: 11.3
• 作者: K. Turk;M. Gradoville;Shunyan Cheung;Francisco M. Cornejo;K. Harding;Michael Mor;o;o;M
• 通讯作者: M