Xenorhabdus Mutualsim and Pathogenesis: Temporal Regulation and Function of Symbiosis Factors

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In symbiotic associations animals, including humans, interact with bacteria that can be either beneficial or harmful. Currently there is limited knowledge of how bacterial adaptation to different host environments dictates whether a particular microbe will cause benefit or harm, despite the important implications of such knowledge in preventing or promoting specific bacterial interactions. This research focuses on understanding how bacteria sense and respond to different host environments to initiate expression of either beneficial or harmful traits. The bacterium being studied expresses beneficial traits when it is associated with a small soil-dwelling roundworm (nematode), and expresses virulence traits when it is associated with insect larvae. As part of its natural life cycle, the nematode transmits (vectors) the bacterium into the insect larva. In this new environment, the bacterium expresses virulence traits, and kills the insect. The insect cadaver then serves as a nutrient source for reproduction and further dissemination of both the nematode and bacteria. This research will examine the complex molecular circuitries that coordinate and regulate the expression of beneficial and harmful traits as the bacteria move between different animal hosts. The paradigms revealed by this research will provide broad insights into such questions as: how does bacterial adaptation to new environments alter symbiotic behavior, and how do vector-borne disease-causing bacteria adapt during transmission by the vector? The results of this research will be published and disseminated to the public through community seminars and high school outreach programs. Undergraduate, graduate, and post-doctoral students will be trained in areas of molecular biology, nematology, entomology, and bacteriology through direct scientific inquiry. Thus, this project will provide fundamental knowledge of bacterial interactions with animal hosts, and will train future scientists with the expertise to further apply this knowledge.