Assessment of Molecular Mechanisms involved in Nitrogen Cost Minimization of Oligotrophic Microorganisms

智力优势：氮成本最小化(减少细胞结构中的氮，特别是蛋白质中的氮)是在低营养水域中茁壮成长的海洋微生物的一种常见和重要的策略。最成功的生物体具有较低的G+C基因组，因此使用侧链中N原子较少的氨基酸，以及这一策略所需的必要权衡--蛋白质平均质量更大(需要更多非限制性碳)，就证明了这一点。该项目的核心假设是，成本最低的生物具有特定的基因组和分子适应，促进氮素节约并保持缓慢而稳定的生长方式。具体地说，这些生物牺牲了潜在的翻译和调控效率，以在任何条件下保持生长。无论底物的可用性如何，它们的生长速度都很慢--在代谢和细胞过程中存在根本限制。据推测，遗传密码中固定的缓慢而稳定的生长可以减少对更复杂的转录调控和复杂的、蛋白质密集型氧化还原反应通路的需求。这项实验计划将通过量化一种在高氮和低氮条件下生长的原氯球菌的初级转录组和局部翻译率来检验这一核心假设。广泛的影响：转录和翻译是帮助设定有机体最大生长速度的基本细胞过程。将应用新技术来捕捉原氯球菌转录格局的详细图片，这有可能产生关于地球上最丰富的微生物之一的成本最小化和转录复杂性之间的关系的变革性信息。该项目期间产生的数据将为许多领域的研究人员提供丰富的资源；该项目期间产生的所有数据都将发布到公共数据库。该项目包括研究生和中学教育部分。广泛的实验室和计算机工作利用尖端实验室和生物信息技术提供了多样化的教育潜力。公众宣传将包括PI和他的实验室继续努力，参与、促进和改善内华达州最贫穷学校的科学教育。这项工作还将有助于进一步发展NSF-EPSCoR基础设施和内华达州的研究活动。

Intellectual Merit: Nitrogen cost-minimization (the reduction of nitrogen in cellular structures, especially protein) is a common and important strategy for marine microbes that thrive in oligotrophic waters. This is evidenced by the most successful organisms having low G+C genomes and thus using amino acids that have fewer N atoms in side chains and by the necessary trade-off this strategy entails - that proteins are, on average, larger in mass (require more non-limiting carbon). This project's core hypothesis is that cost-minimized organisms have specific genomic and molecular adaptations that promote nitrogen thrift and maintain a slow and steady approach to growth. Specifically, these organisms have sacrificed potential efficiencies in translation and regulation to maintain growth under any condition. They grow slowly regardless of substrate availability - there are fundamental limitations in metabolic and cell processes. It is posited that slow and steady growth hard-wired into the genetic code alleviates the need for more complex transcriptional regulation and complex, protein intensive redox sensing pathways. The experimental plan will test this core hypothesis by quantifying the primary transcriptome and local translation rates of a strain of Prochlorococcus grown under high and low nitrogen conditions.Broader Impacts: Transcription and translation are fundamental cellular processes that help set maximum growth rates of an organism. New techniques will be applied to capture a detailed picture of the transcriptional landscape of Prochlorococcus, and this has the potential to yield transformative information on the relationships between cost minimization and transcriptional complexity for one of the most abundant microbes on earth. The data generated during this project will be a rich resource to researchers in many fields; all of the data generated during this project will be released to public databases. This project has graduate and middle school educational components. The extensive laboratory and computer work offers a diverse educational potential using cutting-edge laboratory and bioinformatic techniques. Public outreach will involve a continued effort by the PI and his lab to engage, promote and improve science education in Nevada's poorest schools. This work will also contribute to the further development of the NSF-EPSCoR infrastructure and research activities in Nevada.