Metal composition of marine cyanobacteria - an indicator of niche adaptation and cell physiological state?

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。尽管大量营养素的作用，特别是氮和磷的作用已经得到了先前的关注，但关于控制苦味蓝细菌群落组成的因素的数据仍然相对匮乏。当然，人们对痕量金属在这一过程中的作用知之甚少。因此，我们假设，在海洋生态系统中，遗传上不同的苦味酸细菌因其获取(限制)或调节痕量金属积累(毒性)的能力而受限于特定的生态位。为了解决这一问题，我们建议利用先前的流式细胞仪分选、电感耦合等离子体质谱和X射线显微分析技术，研究海洋原氯球菌和聚球藻代表的微量金属(和大量元素)细胞配额，并评估光胁迫和常量营养素迁移对这些配额的影响；以及ii)天然微藻组合中的微量金属(和大量元素)细胞配额。在这样做时，我们还将第一次获得大空间尺度上的微蓝细菌细胞生理状态的真实指示/实际上使用元素配额作为给定细胞/细胞群体在现场经历的环境的代理/，从而可以实际地开始确定那些可能在原位耗尽并且可能限制生长速度和/或产量的宏元素和微量元素。

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. Athough the role of macronutrients, particularly N and P has received previous attention still there is a relative dearth of data on factors controlling picocyanobacterial community composition. Certainly, little if anything is known of the role of trace metals in this process. Thus, we hypothesise that in oceanic ecosystems genetically distinct picocyanobacteria are restricted to specific niches by their ability to acquire (limitation) or regulate trace metal accumulation (toxicity). In order to address this topic we propose to investigate trace metal (and macroelement) cell quotas in i) representatives of specific marine Prochlorococcus and Synechococcus lineages and to assess the affect of light stress and macronutrient shifts on these quotas and ii) in natural picophytoplankton assemblages using prior flow cytometric sorting, ICP-MS and X-ray microanalysis techniques. In so doing we will also obtain, for the first time, a real indication of picocyanobacterial cell physiological state over large spatial scales / in effect using elemental quotas as a proxy for what environment a given cell/population of cells is experiencing in situ / and hence can realistically begin to determine those macro and trace elements that are potentially depleted in situ and which are potentially restricting growth rate and/or yield.