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

合作研究：通过恒化器和自然种群中的动力学和分子方法评估原绿球藻中的磷状态

• 批准号: 0453029
• 负责人: Gabrielle Rocap
• 金额: --
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2009-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0453029&HistoricalAwards=false
• 关键词: Collaborative; Research; Assessing; phosphorus; status

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.

全球气候变化可能是由人类活动引起的，正在对海洋产生影响。在北太平洋亚热带环流，似乎正在发生向原核生物主导的生态系统的区域转变，部分原因是与气候有关的氮固定增加和随后的磷(P)限制。在这一地区，单细胞海洋蓝藻原氯球菌的数量在过去几十年里一直在增加。目前尚不清楚原氯球菌种群是否受P限制，或者它们在P限制条件下是否具有竞争优势。最近有报道称，在这些磷限制的水域中，原氯球菌的HLII基因占主导地位，并且HLI原氯球菌的存在浓度很低。对无菌HLI和HLII原氯球菌磷利用和磷胁迫响应的研究表明，它们利用有机磷源的能力和碱性磷酸酶活性存在显著差异，而基因组比较显示它们的磷相关基因互补差异不大。这就提出了一个问题，即这两种HL基因的P生理学有什么不同，以及原氯球菌的自然种群是否经历了P限制并利用了有机P。研究人员将在培养分离株和自然种群上进行一项采用生理学和遗传学方法的研究。这些将包括对无菌原氯球菌HL菌株进行P限制摄取动力学研究，以确定它们的相对竞争能力，并检查P相关关键基因在P限制趋化剂中的表达。他们还将进行一项实地研究，通过检查自然种群中的特定基因型基因表达和群落反应以及P-富集瓶实验，确定原氯球菌种群是否以及哪些部分是P-受限的。这项拟议的工作旨在解决一个更大的科学问题的一个方面：是什么环境因素调节着原氯球菌，这是世界上营养最少的海洋中最丰富的浮游植物物种？研究人员将在养殖和自然种群中检测原氯球菌对磷限制的生理和分子反应。这种将传统生理学方法与最先进的分子技术相结合的方法将使人们更好地了解原氯球菌的生态生理学以及天然原氯球菌群的特定基因型的生理状态。归根结底，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调查员以及三名研究生和两所大学的多名本科生的工作。该项目将为USM的本科生提供宝贵的研究和实地经验，USM主要是为缅因州南部地区的非传统学生提供服务的本科机构。通过继续开发新的研究型实验室作业，密歇根州立大学和密歇根大学之间思想和技术的相互交融将对两所院校的课程内容产生直接影响。