Regulatory gene networks and ecological distinctness in marine Synechococcus

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，我们建议采用分子方法来确定特定基因集的调节如何定义这些谱系的生态“独特性”。我们建议将重点放在铁（Fe）的关键营养调节上，因为它们不仅被认为是控制许多海洋环境中初级生产规模的重要资源，而且还因为这些营养物质的浓度在空间和时间上都存在差异，并且与更不稳定（或异质）的沿海水域相比，在更稳定（或均质）的寡营养开放海洋系统中存在明显的“差异”。因此，我们有充分的理由认为，占据不同生态位的世系之间存在着调控能力的差异，而这种调控“约束”，或者实际上缺乏约束，促进了特定生态位（专家）或重叠生态位（机会主义者）的占据。事实上，我们已经观察到，在我的实验室最近注释的海洋聚球菌基因组测序中，缺乏铁获取的关键调控成分，这可能会限制这些分离株在更稳定的环境中。因此，该项目将着手全面了解营养规律，以促进我们认为是专业寡养生物，专业中养生物或机会主义者（即具有不同生活方式的生物）获取这些关键营养物质，我们假设这是他们成功殖民世界海洋大片地区的关键。

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 to identify how regulation of specific gene sets defines the ecological 'distinctness' of these lineages. We propose to focus on the key nutrient regulon of iron (Fe) since not only are these thought to be important resources controlling the magnitude of primary production in many oceanic environments, but also because the concentration of these nutrients varies both spatially and temporally and with obvious 'differences' in more stable (or homogeneous) oligotrophic open ocean systems compared to more unstable (or heterogeneous) coastal waters. Hence, there is strong reasoning to expect that differences in regulatory capacity exist between lineages occupying contrasting niches, and that such regulatory 'constraints', or indeed lack of constraints, facilitate occupation of specific niches (specialists) or overlapping niches (opportunists). Indeed, we have already observed an absence of a key regulatory component for Fe acquisition in sequenced marine Synechococcus genomes my lab has recently been annotating, which may constrain these isolates to more stable environments. Thus, this project will set out to obtain a comprehensive understanding of the nutrient regulons facilitating acquisition of these key nutrients in organisms we consider to be either specialist oligotrophs, specialist mesotrophs or opportunists i.e. with differing lifestyles, which we hypothesise is key to their successful colonization of vast tracts of the world oceans.