Toward Measuring in Situ Growth by Marine Synechococcus: Relationship Between Biochemical Composition, Cell Cycle Regulation, and Growth Rate

聚球藻和原氯球藻是两个密切相关的蓝藻类群的成员，它们在世界海洋中普遍存在并丰富，在许多海洋环境中占初级生产者总生物量和活动的很大比例。这项研究的主要目标是开发非孵化方法来测量自然聚球菌群的原位生长速度。最终，来自这类研究的信息将加强我们对海洋初级生产者群落结构机制的理解，并帮助我们预测环境扰动对这些群落的影响。非孵化生长速率测量的发展需要对感兴趣的生物体中细胞生长和分裂的生理学有透彻的了解。该项目的很大一部分涉及获得海洋聚球藻物种的此类知识。代表性的菌株将在特定的实验室条件下培养。这些条件将有所不同，以实现由各种环境因素控制的一系列增长率。对于在每组条件下生长的每个菌株，平均细胞特征(以及这些特征的种群分布)将通过流式细胞术进行测量。通过这种方式，细胞周期(如DNA分布所反映的)、生化成分和生长速度之间的关系将被建立。这些数据将被用来开发与聚球藻生长速度密切相关的细胞周期或生化指标。最后，这些指数将与测量北大西洋和马尾藻海天然样品增长率的更传统方法进行比较。

Members of two closely related cyanobacterial groups, Synechococcus and Prochlorococcus, are ubiquitous and abundant in the world's oceans, and represent a significant fraction of the overall primary producer biomass and activity in many marine environments. This study has as its major goal the development of non incubation approaches for measuring in situ growth rates of natural Synechococcus populations. Ultimately, the information from such studies will enhance our understanding of the mechanisms by which oceanic primary producer communities are structured, and help us predict the effects of environmental perturbations on those communities. The development of non incubation growth rate measurements requires a thorough knowledge of the physiology of cell growth and division in the organisms of interest. A large part of this project involves gaining such knowledge for marine Synechococcus species. Representative isolates will be cultured under defined laboratory conditions. These conditions will be varied in order to achieve a range of growth rates controlled by a variety of environmental factors. For each strain growing under each set of conditions, average cellular characteristics (and the population distribution of those characteristics) will be measured flow cytometrically. In this way, the relationships between the cell cycle (as reflected in DNA distributions), biochemical composition, and growth rate will be established. These data will be used to develop cell cycle or biochemical indexes that are robustly related to Synechococcus growth rate. Finally, these indexes will be compared with more traditional methods for measuring growth rates in natural samples from the north Atlantic Ocean and Sargasso Sea.