Collaborative Research: Creatine Cycling in Marine Bacterial and Phytoplankton Assemblages

水生系统中溶解有机氮（DON）的产生和利用的高速率通常归因于微生物活动。虽然已知生物有效DON的产生和消耗之间存在紧密耦合，但对这种快速循环DON池的组成、动态和生态意义了解较少。这一建议的重点是DON池的一个组成部分，肌酸，历史上被认为是后生动物活动的产物，但似乎既由浮游植物产生，也被海洋细菌消耗。海水中存在可测量量的肌酸，这导致假设肌酸可能是海洋DON循环的重要组成部分。DON循环可能对基本的海洋生态系统过程产生影响，对全球范围内的碳和氮周转产生重大影响。该项目的更广泛影响将包括通过与俄克拉何马大学（University of Oklahoma）的全州教育研究和发展中心K20教育和社区更新中心合作，为教师和课程开发提供研究经验，将科学家与K-12学生联系起来。本项目将通过海洋科学和微生物生态学的真实研究体验，将研究与农村中学科学教师的探究性教学相结合。K20网络包括俄克拉荷马州96%的学校，为影响俄克拉荷马州的STEM教育提供了独特的机会。该项目的结果将有助于更好地了解DON循环，肌酸摄取活动的生态背景，并确定海洋环境中肌酸产生和消耗的生物。肌酸循环的重要性将通过在北大西洋观察到的沿天然海岸到近海生产力梯度的15N示踪剂研究来评估。示踪剂和分子方法将用于研究浮游植物与细菌在肌酸摄取中的重要性，并通过分子、稳定同位素探测（SIP）和RT-qPCR方法来询问利用细菌的肌酸的分类身份。

High rates of dissolved organic nitrogen (DON) production and utilization in aquatic systems are typically attributed to microbial activity. Though it is known that there is a tight coupling between the production and consumption of biologically available DON, the composition, dynamics, and ecological significance of this rapidly cycled DON pool are less well understood. This proposal focuses on a component of the DON pool, creatine, which is historically understood as a product of metazoan activity, but appears to be both produced by phytoplankton and consumed by marine bacteria. Creatine is present in seawater in measurable quantities, which led to the hypothesis that creatine may be significant component of the marine DON cycle. DON cycling likely has a bearing on fundamental marine ecosystem processes with large implications for carbon and nitrogen turnover on a global scale. Broader impacts of this project will include outreach that focuses on connecting scientists with K-12 students through research experiences for teachers and lesson development in collaboration with the K20 Center for Educational and Community Renewal, a statewide education research and development center at the University of Oklahoma. The project will integrate the research with inquiry-based teaching of rural secondary science teachers through Authentic Research Experiences in oceanographic science and microbial ecology. The K20 network includes 96% of Oklahoma schools, providing a unique opportunity to impact STEM education in Oklahoma.The results of this project will help develop a better understanding of DON cycling, the ecological context of creatine uptake activity, and identify both creatine producing and consuming organisms in the marine environment. The importance of creatine cycling will be assessed via 15N tracer studies along the natural coastal-to-offshore productivity gradient observed in the North Atlantic. Tracer and molecular approaches will be used to investigate the importance of phytoplankton vs. bacteria in creatine uptake and, the taxonomic identities of creatine utilizing bacteria will be interrogated via molecular, stable isotope probing (SIP), and RT-qPCR approaches.