Defining the molecular basis of phylogenetic diversity in marine Synechococcus / a genomic approach

海洋中的光合作用产生了大气中不到一半的氧气。在海洋营养贫乏的中心区域，氧气的生产由非常小的单细胞生物主导，这些生物被称为光合微微型浮游生物。聚球藻属的含藻胆体的单细胞蓝细菌是这种微微型浮游生物部分的主要组成部分，并且在海洋沃茨中具有普遍的分布，在一些区域中负责大约四分之一的初级生产。该属是遗传多样性的，在16S rDNA基因的水平上表现出异质性，迄今为止已经在遗传学上定义了至少10个不同的谱系或分支。我们以前曾提出，这种系统发育异质性的基础上的微妙的生理差异，使特定的谱系占据不同的生态位在水柱。这一想法与我实验室最近的分子生态学工作是一致的，该工作已经证明了这些谱系在原位的不同空间分布，我们认为这类似于占据特定的生态位。为了更全面地了解这种生态位适应的分子基础，我们建议在这里进行基因组的方法来确定我们假设的是定义这些谱系的生态“独特性”的基因集。通过将这项工作与测序基因组的广泛生物信息学分析相结合，我们的目标是全面了解该属基因组进化的机制。

Photosynthesis in the oceans leads to the production of just under half of the oxygen in the atmosphere. In the nutrient-poor central regions of the oceans this production of oxygen is dominated by very small, single celled organisms, which are referred to as the photosynthetic picoplankton. Phycobilisome-containing unicellular cyanobacteria of the genus Synechococcus are a major component of this picoplankton fraction and have a ubiquitous distribution in oceanic waters responsible for around a quarter of the primary production in some regions. The genus is genetically diverse, demonstrating heterogeneity at the level of the 16S rDNA gene, which thus far has phylogenetically defined at least ten distinct lineages or clades. We have previously proposed that this phylogenetic heterogeneity underlies subtle differences in physiology that allow specific lineages to occupy distinct niches in the water column. This idea is consistent with recent molecular ecological work from my lab which has demonstrated distinct spatial distributions of these lineages in situ, which we suggest is akin to occupying specific niches. To more completely understand the molecular basis of this niche adaptation we propose here to undertake a genomic approach to identify what we hypothesise are the sets of genes that define the ecological 'distinctness' of these lineages. By coupling this work to extensive bioinformatic analysis of the sequenced genomes we aim to obtain a comprehensive picture of the mechanisms of genome evolution in this genus.