Collaborative Research and RUI: Assessing phosphorus-status in Prochlorococcus through kinetics and molecular approaches in chemostats and natural populations

可能由人类活动引起的全球气候变化正在对海洋产生影响。 在北太平洋副热带环流，域转移到原核生物为主的生态系统似乎正在发生，部分原因是与气候有关的增加，在N2固定和随后的磷（P）限制。 在这一地区，单细胞海洋蓝细菌原绿球藻的数量在过去几十年中一直在增加。目前尚不清楚原绿球藻种群是否是磷限制的，或者在磷限制的条件下它们是否具有竞争优势。 最近，据报道，原绿球藻的HLII基因型在这些磷限制沃茨中占主导地位，HLI原绿球藻以非常低的浓度存在。 纯HLI和HLII原绿球藻菌株的P利用和P-胁迫反应的研究显示，他们利用有机P源的能力和碱性磷酸酶活性的显着差异，而基因组比较显示，他们的P相关基因的互补差异不大。 这就提出了一个问题是什么区分这两个HL基因型的P生理，以及原绿球藻的自然种群是否经历P限制和利用有机P.研究人员将进行一项研究，采用生理和遗传方法培养的菌株以及自然种群。 这些将包括对原绿球藻纯HL菌株的P限制性摄取动力学研究，以确定其相对竞争能力，并检查P限制性恒化器中关键P相关基因的表达。 他们还将进行一项实地研究，以确定原绿球藻种群是否以及哪些部分是P限制的，通过检查自然种群中的基因型特异性基因表达和社区反应以及P富集瓶实验。 拟议的工作旨在解决一个更大的科学问题的一个方面：什么环境因素调节原绿球藻，世界上贫营养海洋中最丰富的浮游植物物种？研究人员将研究原绿球藻在培养和自然种群中对P限制的生理和分子反应。 这种传统的生理方法与国家的最先进的分子技术相结合，将允许更好地了解原绿球藻的生理生态和天然原绿球藻种群的基因型特异性生理状态。 最终，其目的是将群落结构与生理功能联系起来，并可能与海洋磷循环的变化联系起来。 该项目将支持两名处于学术生涯早期阶段的女性调查员以及两个机构的三名研究生和多名本科生的工作。 该项目将提供宝贵的研究和实地经验，本科生在USM，这主要是一个本科院校，主要服务于南缅因州地区的非传统学生。 USM和UW之间的思想和技术的交叉施肥将通过新的，以研究为基础的实验室作业的持续发展，对这两个机构的课程内容产生直接影响。

Global climate change, likely caused by human activities, is having an impact on the oceans. In the North Pacific Subtropical Gyre, a domain shift to an ecosystem dominated by prokaryotic organisms appears to be occurring due in part to climate-related increases in N2 fixation and subsequent phosphorus (P)-limitation. In this region, populations of the unicellular marine cyanobacterium Prochlorococcus have been increasing over the last several decades. It is not clear whether Prochlorococcus populations are P-limited or whether they have a competitive advantage under conditions of P limitation. Recently it has been reported that the HLII genotype of Prochlorococcus dominates in these P-limited waters, and HLI Prochlorococcus are present in very low concentrations. Studies on P utilization and P-stress response of axenic HLI and HLII Prochlorococcus isolates revealed significant differences in their ability to utilize organic P sources and in alkaline phosphatase activity, whereas a genomic comparison revealed few differences in their complement of P-related genes. This raises the question of what differentiates the P physiology of these two HL genotypes, and whether natural populations of Prochlorococcus experience P limitation and utilize organic P. The investigators will carry out a study employing physiological and genetic approaches on cultured isolates as well as natural populations. These will include P-limited uptake kinetic studies on axenic HL strains of Prochlorococcus to determine their relative competitive ability and examine expression of key P-related genes in P-limited chemostats. They will also carry out a field study to determine if, and which portions of, the Prochlorococcus populations are P-limited through examination of the genotype-specific gene expression and community response in natural populations and P-enrichment bottle experiments. The proposed work is designed to address one aspect of a larger scientific issue: what environmental factors regulate Prochlorococcus, the most abundant phytoplankton species in the world's oligotrophic oceans? The investigators will examine physiological and molecular responses of Prochlorococcus to P-limitation in cultured and natural populations. This combination of traditional physiological methods with state-of-the-art molecular techniques will allow a better understanding of the ecophysiology of Prochlorococcus and the genotype-specific physiological status of natural Prochlorococcus populations. Ultimately, the intent is to relate community structure to physiological function and possibly to changes in the marine P cycle. The project will support the work of two female investigators in the early stages of their academic careers as well as three graduate students, and multiple undergraduates at both institutions. The project will provide valuable research and field experience to undergraduates at USM, which is primarily an undergraduate institution serving mainly non-traditional students in the Southern Maine region. The cross-fertilization of ideas and techniques between USM and UW will have a direct influence on the content of course offerings at both institutions, through continued development of new, research-based laboratory assignments.