Elucidating niche adaptation mechanisms in a ubiquitous marine phototroph: a targeted 'omics approach

海洋在决定世界气候方面起着重要作用。在某种程度上，这是由于非常小的单细胞生物产生氧气和消耗二氧化碳，这些生物被称为光合作用的浮游生物。原绿球藻属和聚球藻属的海洋蓝藻是光合浮游生物的原核成分。我的实验室目前和以前的工作已经证明，这些生物的原位群落结构相当复杂，特定的生态型或谱系占据了不同的生态位，以填充世界海洋，使它们能够在广泛的环境条件下生长和光合作用。虽然这种分子生态学研究可以有效地绘制特定基因型的空间分布，但决定这种全球群落结构的因素仍然模糊不清。这一点很重要，因为主要的picocyanobacterian谱系的变化表明浮游生态系统中主要的领域变化，通过观察和解释它们的分布和生理状态，我们基本上是在评估生物地球化学循环速率的变化。为了更全面地了解这种生态位适应的分子基础，我们建议采用一种以海洋聚球菌为重点的分子方法，以确定特定基因集在定义这些谱系的生态“独特性”方面所起的作用。因此，拟议的项目将寻求对环境（即进化压力）如何塑造重要的海洋光养动物种群基因组提供更基本的理解，从而促进其在首选生态位内的成功。此外，通过对特定环境中表达的基因类型（和丰度）的分析，该项目将有可能提供有关决定这些生物生长速度和产量的关键环境参数的重要新信息，这些信息对于确定海洋光合作用的控制至关重要。

The oceans play a major role in determining the world's climate. In part this is due to the production of oxygen and the consumption of carbon dioxide by very small, single celled organisms, which are referred to as the photosynthetic picoplankton. Marine cyanobacteria of the closely-related genera Prochlorococcus and Synechococcus are the prokaryotic components of the photosynthetic picoplankton. Current and previous work in my lab has demonstrated that the in situ community structure of these organisms is fairly complex, with specific ecotypes or lineages occupying different niches to populate the world's oceans, allowing them to grow and photosynthesise under a broad range of environmental conditions. Whilst such molecular ecological studies can effectively map the spatial distributions of specific genotypes, the factors that dictate this global community structure are still poorly defined. This is important because changes in dominant picocyanobacterial lineages indicate major domain shifts in planktonic ecosystems and by observing and interpreting their distributions and physiological states we are essentially assessing changes in the rates of biogeochemical cycles. To more completely understand the molecular basis of this niche adaptation we propose here to undertake a molecular approach focusing on marine Synechococcus so as to identify the role that specific gene sets play in defining the ecological 'distinctness' of these lineages. The proposed project will thus seek to provide a more fundamental understanding of how the environment (i.e. evolutionary pressure) shapes the population genome of an important marine phototroph, so facilitiating its success within its preferred ecological niche. Moreover, via analysis of the types (& abundance) of genes expressed in specific environments the project will potentially provide important new information on the key environmental parameters that dictate the growth rate and yield of these organisms, information which is critical for defining controls on marine photosynthesis.