Regulatory gene networks and ecological distinctness in marine Synechococcus

海洋在决定世界气候方面发挥着重要作用。这在一定程度上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微浮游生物。海洋蓝藻是原氯球藻属和聚球藻属的近缘属，是光合作用微微浮游生物的原核成分。我实验室目前和以前的工作已经证明，这些生物体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来繁殖世界海洋，使它们能够在广泛的环境条件下生长和光合作用。虽然这样的分子生态学研究可以有效地绘制特定基因类型的空间分布图，但决定这种全球群落结构的因素仍然定义不清。这一点很重要，因为优势异氰化细菌谱系的变化表明浮游生态系统中的主要区域发生了变化，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，我们建议在这里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)的关键营养调控上，因为铁不仅被认为是控制许多海洋环境中初级生产力大小的重要资源，而且这些营养物质的浓度在空间和时间上都是不同的，与更不稳定(或不均匀)的沿海水域相比，在更稳定(或同质)的寡营养开阔海洋系统中存在明显的“差异”。因此，有很强的理由认为，在占据着截然不同的利基市场的不同血统之间存在监管能力的差异，这种监管‘约束’，或者实际上缺乏约束，会促进占据特定的利基市场(专家)或重叠的利基市场(机会主义者)。事实上，我们已经观察到在测序的海洋聚球藻基因组中缺乏铁获取的关键调控成分，我的实验室最近一直在注释，这可能会限制这些分离物到更稳定的环境中。因此，这个项目将着手全面了解促进这些关键营养物质在生物体中获得的营养调节，我们认为这些生物体要么是专业寡养生物，要么是专业中营养生物，要么是具有不同生活方式的机会主义者，我们假设这是它们成功地在世界海洋大片海域殖民的关键。

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.