Unveiling the contributions and regulation of picoeukaryotic phytoplankton in oceanic environments.

海洋初级生产者的增长率和命运是调节生物圈碳通量的关键因素。虽然已知资源限制起着重要的调节作用，但控制微藻(直径2微米)生长和死亡的具体因素却知之甚少。特别是，由于这些占主导地位的初级生产者规模小，沉降商低，它们在水柱中的去向和迁移的决定因素对于开发碳通量及其可能因气候变化而产生的扰动的预测模型至关重要。浮游微藻由蓝藻、(原氯球菌和聚球藻)和小型真核生物组成。虽然微蓝细菌受到了广泛的关注，但对微藻真核生物的分布和动态，特别是在海洋环境中的分布和动态知之甚少。到目前为止所做的几项比较测量表明，微藻真核生物的生产力可以与微囊藻相媲美。因此，迫切需要了解微藻真核生物在开阔海洋环境中的作用。然而，这种知识只有放在浮游微藻总群落的背景下才有价值，因此，也必须包括对微蓝细菌的量化。总体目标是开发一种确定微藻真核生物潜在生理控制的方法。将使用一种有针对性的方法，结合流动排序、cDNA文库和表达序列标签(EST)，从而能够识别实时表达反应。这一知识将突出有关微真核生物种群动态的关键生理限制和分子基础信息，并有助于未来分离远洋微真核生物的努力。这是这项工作的一个重要的额外好处，因为环境克隆文库数据表明，这种微真核生物在培养样本中的代表性很差。从长远来看，开发的环境基因组方法还将提供一个高通量机制，用于在该领域中分析表达反应(MRNA)。在这项拟议的工作中，将评估赤道大西洋和南太平洋两个大洋盆地的表达反应。更广泛的影响。用来阐明对环境胁迫因子的实时反应的实验功能基因组学方法适用于所有真核生物，对其他寻求确定原位反应的分子基础的微生物生态学家也有价值。此外，来自未培养的微真核生物的序列，再加上分子系统学的进展，导致了对真核进化的戏剧性的重新考虑；这里产生的序列应该有助于改进进化研究和“生命树”。该项目将为几个教育级别的学生提供培训，包括高危少数民族高中生、本科生和两名博士生。来自该项目的信息将被纳入海洋微生物生态学研究生和本科生水平的课程(由海洋微生物生态学研究所教授)。项目成果将通过两种基于互联网的格式提供，一种是为普通公众量身定做的，另一种是为科学界定制的。

The growth rates and fate of primary producers in the oceans are key factors regulating carbon flux in the biosphere. While resource limitation is known to play a major regulatory role, the specific factors controlling growth and mortality of picophytoplankton (2 microm diameter) are poorly understood. In particular, due to the small size and low sinking quotient of these dominant primary producers, determinants of their fate and transport in the water column are critical to the development of predictive models of carbon flux and its likely perturbation due to climate change. Picophytoplankton is composed of cyanobacteria, (Prochlorococcus and Synechococcus) and small eukaryotes. While the picocyanobacteria have received much attention, little is known about the distribution and dynamics of picophytoeukaryotes, particularly in oceanic settings. The few comparative measurements made to date indicate that the productivity of picophytoeukaryotes can rival that of picocyanobacteria. Hence, knowledge regarding the role of picophytoeukaryotes in open ocean environments is urgently needed. However, this knowledge is only valuable when put in the context of the total picophytoplankton community and, therefore, quantification of picocyanobacteria must be also be included. The overall goal is to develop a method for determining underlying physiological controls of picophytoeukaryotes. A targeted approach will be used, combining flow sorting, cDNA libraries and Expressed Sequence Tags (EST), allowing real-time expressional responses to be identified. This knowledge will highlight key physiological constraints and information on molecular underpinnings of picoeukaryotic population dynamics as well as aiding future efforts to isolate open-ocean picoeukaryotes. This is an important additional benefit from the work since environmental clone library data has demonstrated that such picoeukaryotes are poorly represented in culture collections. Long-term, the environmental genomic approach developed will also provide a high throughput mechanism for profiling expressional responses (mRNA) in the field. In the proposed work, expressional responses will be evaluated in two ocean basins, the equatorial Atlantic and the South Pacific. Broader Impacts. The experimental functional genomics approach taken to elucidate real-time responses to environmental forcing factors is applicable to all eukaryotes, and of value to other microbial ecologists seeking to identify molecular underpinnings of in situ responses. Moreover, sequences derived from uncultured picoeukaryotes, in combination with advances in molecular phylogeny, have led to a dramatic reconsideration of eukaryotic evolution; the sequences generated herein should aid refinement of evolutionary studies and the "Tree of Life". The project will provide training for students at several educational levels, including at-risk minority high school students, undergraduates and two Ph.D. candidates. Information from the project will be incorporated into graduate and undergraduate level courses on Marine Microbial Ecology (taught by the PI). Project results will be available via two internet based formats, one tailored to the general public and one for the scientific community.