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Oral: Bacterial Virulence Regulation


Integration of plant host-derived signals to coordinate developmental processes involved in Pantoea stewartii subsp. stewartii biofilm maturation.
M. ROPER (1), M. Roper (1) (1) University of California, Riverside, U.S.A.

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Participation in complex, multicellular cooperative communities, known as biofilms, is a universal attribute of bacteria. Biofilm formation is now a major tenet of microbiology, yet we know little information about what environmental and physical cues drive biofilm formation in a natural context, such as during bacterial infection processes. Biofilms are encased in an extracellular matrix consisting primarily of exopolysaccharide (EPS), which holds these biofilms together, providing robustness to the architecture and making them difficult to clear from the host. The focus of this project is on the xylem-dwelling bacterium, Pantoea stewartii subsp. stewartii (Pss)/sweet corn pathosystem. We have placed our attention on the multi-component Rcs signal transduction system, an environmental sensing system found in Pss and other enteric bacteria. This system controls genes related to biofilm formation, namely EPS matrix production. We demonstrate that host plant-derived reactive oxygen species (ROS) are one environmental signal that modulates the Rcs system and this stimulation is dependent on the redox sensing transcription factor, OxyR. In addition, we demonstrate a link between a novel RTX-like, cytolytic protein in lysing host plant cells, releasing ROS and stimulating the Rcs system and subsequent EPS production, thus aiding in transition between the apoplastic and xylem phases of Stewart’s wilt disease.