Collaborative Research: Prochlorococcus and its contribution to new production in the Sargasso Sea

合作研究：原绿球藻及其对马尾藻海新产品的贡献

• 批准号: 0928544
• 负责人: Adam Martiny
• 金额: $ 65.78万
• 依托单位: University of California-Irvine
• 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: 2009-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0928544&HistoricalAwards=false
• 关键词: Collaborative; Research; Prochlorococcus; its; contribution

The cyanobacterium Prochlorococcus marinus is ubiquitous in the oligotrophic subtropical and tropical oceans and can contribute up to 82% of the primary productivity in certain regions. In contrast to most other phytoplankton, cultured Prochlorococcus isolates cannot assimilate NO3-. However, Lomas' group has used flow cytometry and stable isotope tracers to demonstrate direct NO3- assimilation by Prochlorococcus in the Sargasso Sea. In support of these findings, Martiny and colleagues have shown that Prochlorococcus cells residing in the mixed layer carry genes for NO2- and NO3- assimilation, and that these genes are functional and expressed in field populations. The combined results suggest that uncultured lineages of Prochlorococcus are capable of NO3- assimilation and can contribute to new production in many oceanic regions - but the overall significance is yet unknown. The overarching hypothesis of this project is that cell-specific NO3- assimilation rate is a function of both the ambient nutrient concentrations and the metabolic potential of the cell (i.e. presence of genes encoding for NO2- and NO3- assimilation). The specific research questions of this project are: 1) Is NO3- a quantitatively important nutrient source for Prochlorococcus and does Prochlorococcus contribute to new production? 2) What is the influence of seasonal and vertical variation in nitrogen substrates (NH4+, urea, NO2-, andNO3-) on the genome content of Prochlorococcus and oxidized nitrogen uptake rates? To answer these questions, PIs will use the combination of high-sensitivity nutrient measurements, a flow cytometric assay developed by Lomas to quantify nitrogen assimilation in specific taxonomic groups, and metagenomics and a qPCR assay to determine the occurrence of nitrite (nirA) and nitrate reductase (narB) genes associated with Prochlorococcus. Using these tools, they will quantify NO3- assimilation and the distribution of NO3- assimilation genes in Prochlorococcus through three full seasonal cycles and over the entire euphotic zone. In addition, these direct measurements will be augmented by manipulative mesocosm experiments (reciprocal transplant and nutrient addition experiments) to explicitly test aspects of their hypotheses. The PIs hope to achieve a mechanistic understanding of direct (variations in the concentration of nitrogen species) and indirect controls (genomic adaptation in Prochlorococcus) on NO3- assimilation rates. One of the most exciting outcomes from this project will be a more complete understanding of the nutritional ecology of Prochlorococcus in field assemblages. The PIs have selected to conduct this study in the Sargasso Sea, because of the wealth of necessary supporting data and logistical infrastructure that this site provides, and because they have already shown that Prochlorococcus is capable of nitrate assimilation in this region. Broader Impacts: This project will have broader impacts on many levels. First, the potential for previously unrecognized widespread productivity by Prochlorococcus fueled byNO2- and NO3- assimilation has significant implications for the understanding of the biogeography of Prochlorococcus and its role in oceanic carbon and nitrogen cycles. Secondly, it will exemplify how genome evolution, cell physiology, and environmental variables interact to shape the biogeochemical role of bacteria in the ocean. The PIs will present their results in a manner that can be easily incorporated in biogeochemical and ecosystem models, including those related to changes in regional and global biological processes in response to climate-driven variability. This project will provide research opportunities for graduate (one at UCI) and undergraduate students. This project will also establish an internationally linked education outreach program to provide high school teachers and students in California and Bermuda with hands-on experience in marine microbial ecology and its relationship to global ocean processes and biogeochemistry.

氰基核球菌在贫营养的亚热带和热带海洋中无处不在，在某些地区可贡献多达82％的主要生产力。与大多数其他浮游植物相比，培养的核球菌分离株不能同化NO3-。然而，洛马斯的组使用流式细胞术和稳定的同位素示踪剂来证明萨尔加索海中核酸菌群直接同化。为了支持这些发现，Martiny及其同事表明，居住在混合层中的氯环球细胞携带基因以no2和No3-同化，并且这些基因具有功能性并在田间种群中表达。综合结果表明，未培养的核球菌谱系能够同化，并且可以在许多海洋地区有助于新生产 - 但总体意义尚不清楚。 该项目的总体假设是细胞特异性的NO3-同化率是环境营养浓度和细胞代谢潜力的函数（即存在编码NO2-和NO3-同化的基因）。 该项目的具体研究问题是：1）NO 3-是核酸核酸的数量上重要的营养来源，而核酸核酸菌属是否有助于新产量？ 2）氮底物（NH4+，尿素，NO2-和NO3-）对季节性和垂直变化的影响对氯球菌的基因组含量以及氧化的氮摄取速率有什么影响？为了回答这些问题，PI将使用高敏感性营养测量值的组合，这是Lomas开发的流式细胞仪测定法，以量化特定分类学组中的氮同化，宏基因组学和QPCR测定法来确定与氮（NIRA）（NIRA）和硝酸盐的发生相关的氮（Narbe Reduct）（narb）基因（NARBERCASE（NARBER））。使用这些工具，它们将通过三个完整的季节性周期和整个舒适区域量化NO3-同化和NO3同化基因的分布。此外，这些直接测量将通过操纵中的实验（相互移植和养分添加实验）来增强，以明确测试其假设的方面。 PI希望对直接（氮种的浓度的变化）和间接对照（基因组适应）在NO3同化速率上实现机械理解。该项目中最令人兴奋的结果之一将是对现场组合中核酸核酸的营养生态学的更全面了解。由于本网站提供的大量支持数据和后勤基础设施，PIS选择了在Sargasso Sea进行这项研究，并且由于它们已经表明prochlorococcus能够在该地区硝酸盐同化。 更广泛的影响：该项目将对许多层面产生更广泛的影响。首先，通过NO2-和NO3-同化的核酸核酸群的先前未认识到的广泛生产力的潜力对理解pro氯环球的生物地理及其在海洋碳和氮气周期中的作用具有重要意义。其次，它将举例说明基因组进化，细胞生理和环境变量如何相互作用以塑造细菌在海洋中的生物地球化学作用。 PI将以可以轻松纳入生物地球化学和生态系统模型的方式呈现其结果，包括与气候驱动的变异性响应区域和全球生物过程变化相关的结果。该项目将为研究生（UCI）和本科生提供研究机会。 该项目还将建立一项与国际联系的教育外展计划，为加利福尼亚和百慕大的高中教师和学生提供海洋微生物生态学方面的动手经验，以及与全球海洋过程和生物地球化学的关系。