Marine Synechococcus Ecotypes: Seasonal and Spatial Distributions of Physiological and Genetic Diversity

该项目将探讨海洋蓝细菌聚球藻的遗传和生理多样性，聚球藻是世界贫营养海洋初级生产的主要贡献者。 除了在贫营养海洋中的作用外，聚球藻还可以在中营养和富营养沃茨中发现。 这与仅限于亚热带开阔海洋的密切相关的原绿球藻属的成员形成鲜明对比。 目前尚不清楚聚球藻属范围的增加是否反映了该属所有菌株的更广泛的生理耐受性，或者是否存在特别适应更高营养和更冷温度条件的生态型。 在聚球藻群落如何应对全球气候变化或沿海沃茨富营养化等环境条件变化方面，这些交替的情景具有非常不同的影响。 在这个项目中，这个问题正在解决两种方式，通过表征聚球藻的多种基因型的生理学，并通过确定这些基因型在来自地球仪的水样中的季节丰度。 海洋聚球藻由许多（七个或更多）遗传上不同的谱系组成。 这些谱系中的三个与特征生理学（运动性、色适应性和缺乏藻胆素）特别相关，第四个由不能利用硝酸盐作为氮源的单一菌株组成。 然而，与其他三种基因型相关的生理学尚未确定。 为了开始了解聚球藻属所有基因型对可能影响其生长和分布的因素的生理反应，在该项目中，每个遗传分支的几个代表性菌株在一系列光照水平、温度和氮源下生长。 一些证据表明，自然界中存在着其他的遗传谱系，但尚未被培养。 为了进一步探讨这一点，在公海聚球藻种群在大西洋和太平洋和沿海人口在普吉特湾，华盛顿的遗传多样性正在检查的终端限制性片段长度多态性和16 S-23 S核糖体RNA内部转录间隔区（ITS）的测序分析。 使用这些序列和已经从聚球藻分离株中确定的序列，将设计对每个遗传进化枝特异的引物。 这些引物将用于来自相同三个环境的一组每月样本的实时定量PCR，以量化两个年度周期内每种遗传类型的丰度。 这个项目将直接涉及一个研究生和一个或多个本科生。 在普吉特海湾建立一个研究项目，通过UW海洋学院的高级实地课程为更多的本科生提供参与的机会。 此外，关于普吉湾聚球藻分布和动态的数据将与华盛顿州生态部分享，并纳入普吉湾食物网模型。 最后，检查全球分布和人口动态的聚球藻结合实验测量的生长，每种基因型的一套物理条件下，将提供见解的相对重要性，生态分化和生理可塑性，在确定这些分布。

This project will explore the genetic and physiological diversity of the marine cyanobacteria Synechococcus, which are major contributors to primary production in the world's oligotrophic oceans. In addition to its role in the oligotrophic oceans, Synechococcus can also be found in mesotrophic and eutrophic waters. This is in sharp contrast to the members of the closely related genus Prochlorococcus that are restricted to the subtropical open oceans. At present it is not clear if the increased range of Synechococcus reflects a broader physiological tolerance by all the strains of this genus, or the existence of ecotypes that are specifically adapted to higher nutrient and colder temperature conditions. These alternate scenarios have very different implications in terms of how the Synechococcus community may respond to changes in environmental conditions such as global climate change or eutrophication of coastal waters. In this project, this question is being addressed two ways, by characterizing the physiology of multiple genotypes of Synechococcus, and by determining the seasonal abundances of these genotypes in water samples from around the globe. It has been established that marine Synechococcus consists of a number (seven or more) of genetically distinct lineages. Three of these lineages are specifically associated with a characteristic physiology (motility, chromatic adaptation and lack of phycourobilin), and a fourth consists of a single strain which is incapable of utilizing nitrate as a nitrogen source. However, the physiologies associated with the other three genotypes have not yet been determined. To begin to understand physiological responses of all of the genotypes of Synechococcus to factors that are likely to influence their growth and distributions, in this project, several representative strains of each genetic clade are being grown in a range of light levels, temperatures and nitrogen sources. Several lines of evidence suggest that additional genetic lineages exist in nature but have not yet been cultivated. To explore this further, the genetic diversity in open ocean Synechococcus populations in the Atlantic and Pacific and coastal populations in Puget Sound, Washington are being examined by terminal Restriction Fragment Length Polymorphism and sequencing analyses of the 16S-23S ribosomal RNA internal transcribed spacer (ITS). Using these sequences and those already determined from Synechococcus isolates, primers will be designed that are specific for each of the genetic clades. These primers will be used in real-time quantitative PCR in a set of monthly samples from the same three environments to quantify the abundance of each genetic type over two annual cycles. This project will directly involve a graduate student and one or more undergraduate students. Establishing a research program in Puget Sound is providing opportunities for additional undergraduate involvement through the UW School of Oceanography senior field course. In addition, data on Synechococcus distributions and dynamics in Puget Sound will be shared with the Washington State Department of Ecology and incorporated into a Puget Sound food web model. Ultimately, examining the global distribution and population dynamics of Synechococcus in conjunction with experiments measuring the growth of each genotype under a suite of physical conditions will provide insights into the relative importance of ecotypic differentiation and physiological plasticity in determining these distributions.