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

两种密切相关的蓝藻群，聚藻球菌和原绿球藻，在世界海洋中无处不在，数量丰富，在许多海洋环境中代表了总体初级生产者生物量和活动的重要组成部分。本研究的主要目标是发展非孵育方法来测量天然聚囊球菌种群的原位生长速率。最终，来自这些研究的信息将增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。非孵育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。这个项目的很大一部分涉及获取海洋聚囊球菌物种的知识。有代表性的分离株将在规定的实验室条件下培养。这些条件将会变化，以达到由各种环境因素控制的一系列增长率。对于在每种条件下生长的每种菌株，流式细胞术将测量平均细胞特征（以及这些特征的种群分布）。通过这种方式，将建立细胞周期（反映在DNA分布上）、生化组成和生长速率之间的关系。这些数据将用于开发与聚囊球菌生长速率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自然样本生长速率的更传统的方法进行比较。

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.