Collaborative Research: Host specificity strategies in a binary mutualism: physiological and molecular processes and evolutionary relationships

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All plants and animals, including humans have evolved to live in symbiotic association with microbes. At the cellular level, complex molecular circuitries monitor microbial populations and respond to either defend against harmful microbes, or recruit and maintain beneficial microbes. Current scientific knowledge is limited with regard to how animals distinguish among different microbes, enabling them to selectively recruit or restrict microbial colonization. This research focuses on understanding how bacterial symbionts interact with and affect their animal hosts, and how these interactions influence the evolution of inter-species cooperation. Three investigators with complementary expertise will conduct collaborative research on small soil-dwelling roundworms (nematodes) that have evolved mutually beneficial associations with a specific group of bacteria. Together the nematodes and bacteria form insecticidal complexes effective against a wide range of insect hosts, from which they derive nutrients for reproduction and dissemination. These associations involve different species of nematodes and bacteria, and current research indicates that different combinations have evolved varying degrees of dependence on each other. Research on these cooperative associations is poised to yield insights into the processes influencing selectivity and function of microbial symbioses. To help achieve this potential, this multidisciplinary research team will investigate for the first time specific bacterial traits contributing to host fitness in this system. Such knowledge will be critical to our understanding of the selective pressures influencing the evolution of specialized versus generalized associations between mutually benefiting partners. High school, undergraduate, graduate, and post-doctoral students at the three collaborating institutions will be trained in the areas of evolution, molecular biology, nematology, entomology, and bacteriology through direct scientific inquiry. Thus, this project will provide fundamental insights into the ubiquitous process by which animals recognize, maintain, and benefit from their beneficial microbial partners, and will help train future scientists with the expertise to further apply this knowledge.