EAGER: Competition and interactions among predators of bacteria in microbial loop dynamics

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The National Science Foundation uses the Early-concept Grants for Exploratory Research (EAGER) funding mechanism to support exploratory work in its early stages on untested, but potentially transformative, research ideas or approaches. This EAGER project was awarded as a result of the invitation in the Dear Colleague Letter NSF 16-080 to proposers from Historically Black Colleges and Universities to submit proposals that would strengthen research capacity of faculty at the institution. The project at Florida Agricultural and Mechanical University aims to study the ecological role of predatory bacteria, Bdellovibrio-like organisms (BALOs), in marine waters. The project outcome can reveal interactions not only amongst the bacterial predators but also among the predators and their prey bacteria under various environmental factors. The scientific objectives of this study are to: investigate how viruses, Halobacteriovorax, and heterotrophic protists effect one another in decreasing bacterial abundance; quantify the relative proportion of all three mortality mechanisms on bacterial loss; determine environmental effects on predatory activities of protists, viruses, and Halobacteriovorax; and model population dynamics of predators and prey. The approach to accomplishing these objectives is to measure loss rates of a virus, heterotrophic protist, and a Halobacteriovorax on the mortality of bacteria in laboratory microcosms and field studies. The novelty and innovativeness of this approach is that while many of these components have been examined independently, this would be the first time that mortality is quantitatively partitioned for this complex system. The expected high-payoff from this innovative Early-Concept for Exploratory Research project is transformative results that dramatically increase understanding of tri-trophic planktonic interactions that significantly influence oceanic biogeochemical fluxes of carbon and nutrients through the microbial loop and reveal Halobacteriovorax as a major bacterial predator.