Excellence in Research: Assessing the Control by Multiple Micropredators on Bacterial Communities in Estuarine Environments and Characterization of Prey Lysis Products Resulting fr

微生物是地球上数量最多的生物，在环境中扮演着降解、循环养分的重要角色。细菌过多或过少都可能破坏敏感的生态平衡和碳、氮、磷循环等环境过程的正常运作。在任何给定的环境中，细菌种群的丰度是由各种生物、化学和物理机制控制的。生物制剂中有细菌的微观捕食者或微捕食者。其中研究最多的是原生生物，感染细菌的病毒，以及一组被统称为蛭弧菌及其类生物（BALOs）的细菌。这些微型捕食者捕食某些细菌，以获取繁殖所需的营养物质或其他细胞物质。在这个过程中，被捕食细菌的细胞产物被释放到环境中，并被其他微生物用作营养物质。尽管这些微型捕食者在自然界中共同出现，并且可能相互作用，但大多数实验研究都是单独调查它们的活动，而不是集体调查。因此，人们对它们在控制细菌数量和养分循环中的共同作用知之甚少。拟议研究的目标是通过在模拟的自然条件下将这三者作为一个集体进行调查，以解决这一知识上的差距，这些自然条件代表了一系列的温度、盐度和猎物的丰度。该项目在两所历史悠久的黑人大学（HBCUs）进行，这些大学在培训和指导来自科学领域代表性不足的学生和博士后方面有着良好的记录。该项目通过为本科生和研究生以及早期职业科学家提供独特而有意义的教育和研究培训经验，使多达100名学生受益。具体活动包括关于科学写作和在年度项目讲习班以及国家和国际科学会议上展示成果的课程。研究生们正在接受化学和微生物学方面现代先进方法的培训。有一个持续的评估模块来记录教育和培训成果。目前公认的两种细菌死亡机制是异养原生生物放牧和病毒感染。越来越明显的是，一组研究不足的掠食性细菌BALOs也可能导致细菌死亡。然而，balo -猎物相互作用的动力学机制尚不清楚，微捕食者、balo、原生生物和细菌病毒之间的相互作用也是如此。最终，这些过程可能对微生物环的结构和功能产生不同的影响，包括影响更高的营养水平和生物地球化学循环。研究人员假设，环境因素显著影响了细菌种群的死亡率在微捕食者之间的分配。为了验证这一假设，研究人员正在(1)研究微捕食者之间的相互作用，(2)通过NMR/ FT-ICR质谱（MS）混合方法研究溶解有机物的分子水平组成和动力学，作为不同死亡过程的结果，以及(3)模拟这些三营养动力学。智力价值：本研究的结果将定义影响微生物环和海洋生物地球化学循环的死亡动力学的新机制理解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Microbes are the most abundant organisms on Earth and play an important role as degraders, cycling nutrients in the environment. Too many or too few bacteria may disrupt a sensitive ecological balance and proper functioning of environmental processes such as carbon, nitrogen and phosphorus cycles. The abundance of bacteria populations in any given environment is controlled by various biological, chemical and physical mechanisms. Among the biological agents are microscopic predators, or micropredators, of bacteria. The most studied of these are protists, viruses that infect bacteria, and a group of bacteria collectively known as the Bdellovibrio and like organisms (BALOs). These micropredators prey upon certain bacteria to obtain required nutrients or other cellular material for their replication. In the process, cellular products from the prey bacteria are released into the environment and utilized as nutrients by other microbes. Although the micropredators co-occur, and likely interact, in nature, most experimental studies have investigated their activities individually, rather than collectively. As a result, little is known about their collective role in controlling bacteria populations and the cycling of nutrients. The goal of the proposed research is to address this gap in knowledge by investigating all three as a collective group under simulated natural conditions representing a range of temperature, salinity and abundance of prey. This project is conducted at two Historically Black Universities (HBCUs) with strong records of training and mentoring students and postdocs from underrepresented populations in science. The project benefits up to 100 students by providing unique and meaningful educational and research training experiences at the undergraduate and graduate student levels and for early-career scientist. Specific activities include courses on scientific writing and presenting results at annual project workshops as well as national and international scientific meetings. Graduate students are being trained in modern advanced methodologies in chemistry and microbiology. There is an ongoing assessment module to document education and training outcomes.Up to now, the two mainly accepted mechanisms of mortality in bacterial populations are heterotrophic protist grazing and viral infection. Increasingly, it has become evident that an understudied group of predatory bacteria, BALOs, can also contribute to bacterial mortality. Yet, the mechanisms underlying the dynamics of BALO-prey interactions are poorly understood, as are the interactions among the micropredators, BALOs, protists and bacterial viruses. Ultimately, these processes may have contrasting influences on the structure and functioning of the microbial loop, including impacting higher trophic levels and biogeochemical cycles. The investigators hypothesize that environmental factors significantly influence how mortality in bacterial populations is partitioned among the micropredators. To test this hypothesis researchers are (1) investigating the interactions amongst the micropredators, (2) examining the molecular-level composition and dynamics of dissolved organic matter as the result of the different mortality processes by the NMR/ FT-ICR mass spectrometry (MS) hybrid approach, and (3) modeling these tri-trophic dynamics. Intellectual Merit: Results from this research will define a new mechanistic understanding of mortality dynamics that influence the microbial loop and oceanic biogeochemical cycles.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.