The role of iron (Fe) in controlling in situ distributions and activities of marine synechococcus

单细胞蓝藻聚藻球菌是海洋环境中最丰富的初级生产者之一。它也非常普遍；在开阔的海洋、沿海甚至极地环境中都发现了聚囊球菌。与其近亲原绿球藻（Prochlorococcus）不同，聚球菌（Synechococcus）具有利用NO3的能力，并在野外对NO3的输入作出反应，这表明该生物可能在全球碳循环，特别是新生产中发挥关键作用。到目前为止，已经确定了16个潜在的分支，人们认为这种高度的多样性允许聚珠球菌辐射到许多不同的环境条件。然而，尽管聚珠球菌的普遍存在和丰富，很少有研究表征每个分支的生理和生态位适应。铁（Fe）作为生态位适应的决定性因素显示出巨大的潜力，因为它的浓度在聚球菌的地理范围内以及每年在特定地点有所不同，并且已被证明限制了开放海洋和沿海环境中的初级生产。此外，培养工作表明，聚球菌菌株在低浓度铁条件下具有不同的生长能力。通过对现有海洋聚球菌基因组的比较，发现与铁胁迫相关的已知基因存在或缺失具有很大的多样性，这表明铁可能在聚球菌的多样化和生态位适应中发挥了关键作用。本项目将研究铁对11个不同聚球菌支系生长和固碳的影响（每个支系尽可能使用至少2个菌株），以及铁限制在确定聚球菌支系时空分布中的作用。本项目将为聚球菌铁特异性生态位分化的影响提供全面和系统的数据集，为控制进化支分布的因素提供新的见解，并为聚球菌多样性的生物地球化学后果提供理解。更广泛的影响除了在实验室和现场确定铁限制对海洋聚球菌的作用和影响外，该项目还将开发基于pcr的定量铁胁迫诊断方法，供社区使用。这些数据还将允许改进浮游植物群区分模式的参数化，从而提高预测生物地球化学循环动态的能力。这项研究的结果将在国家会议上广泛传播。此外，该项目将完全资助博士后Jill A Sohm博士和两名参加暑期研究的本科生，并为他们提供宝贵的研究经验和职业发展。

The unicellular cyanobacterium Synechococcus is one of the most abundant primary producers in the marine environment. It is also extremely widespread; Synechococcus has been found in open ocean, coastal and even polar environments. Unlike its close relative, Prochlorococcus, Synechococcus has the ability to use NO3 and has been shown to respond in the field to NO3 inputs, suggesting that this organism may play a key role in global carbon cycling and especially new production. To date, 16 potential clades have been identified, and it is thought that this high diversity allows for the radiation of Synechococcus into many different environmental conditions. However, despite the ubiquity and abundance of Synechococcus, there are few studies characterizing the physiology and niche adaptations of each clade. Iron (Fe) shows great potential as a defining factor for niche adaptations, as its concentration varies over the geographic range of Synechococcus, as well as annually at specific locations, and has been shown to limit primary production in both open ocean and coastal settings. In addition, culture work indicates that Synechococcus strains have different abilities to grow on low concentrations of Fe. A comparison of the available genomes of marine Synechococcus shows great diversity in the presence or absence of known genes related to Fe stress, suggesting that Fe could have played a key role in the diversification and niche adaptation of Synechococcus. This project will study the effects of Fe on growth and carbon fixation in 11 different clades of Synechococcus (using at least 2 strains from each clade whenever possible) and the role of Fe limitation in determining the distribution of Synechococcus clades on temporal and spatial scales. This project will produce a comprehensive and systematic data set on the impact of Fe-specific niche differentiation in Synechococcus, offer new insight into the factors that control clade distribution, and provide understanding of the biogeochemical consequences of Synechococcus diversity. Broader Impacts In addition to defining the role and impact of Fe limitation on marine Synechococcus, both in the lab and in the field, this project will develop quantitative PCR-based Fe stress diagnostics that will be available to the community. These data will also allow for improved parameterization of models in which phytoplankton groups are differentiated, therefore improving the ability to predict the dynamics of biogeochemical cycles. The results of this research will be widely disseminated at national conferences. Furthermore, this project will completely fund and provide valuable research experience and career development for post-doctoral fellow Dr. Jill A Sohm, as well as two undergraduates participating in summer research.