FBS Colloquia No.412Laboratory of Nano-Biophysics

Repellent Responses of Vibrio Species and Intracellular Dynamics of the Signaling Protein CheY

Marine Vibrio species are bacteria that grow in seawater and exhibit two distinct lifestyles: (1) a free-living lifestyle in seawater and (2) a symbiotic lifestyle in which they attach to the surfaces of fish and other marine organisms. In addition, the genus Vibrio includes pathogenic species, such as Vibrio cholerae and Vibrio parahaemolyticus. Marine Vibrio species has a single polar flagellar motor, a rotary apparatus, at one cell pole. The flagellum rotates in both counterclockwise (CCW; forward swimming) and clockwise (CW; backward swimming) directions. By regulating the frequency of forward and backward swimming, Vibrio cells are able to move toward more favorable environments. As in the well-studied bacterium Escherichia coli, the direction of motor rotation in marine Vibrio is controlled by the direct binding and dissociation of the intracellular signaling molecule phosphorylated CheY. However, in marine Vibrio, a quantitative understanding of chemotactic protein dynamics in response to extracellular stimuli remains elusive. In this study, to quantify the intracellular dynamics of the signaling molecule CheY, we developed CheY-GFP fusion and analyzed its intracellular behavior using a high-throughput measurement system, which was recently developed in our laboratory. We simultaneously measured the dynamics of CheY-GFP in hundreds of Vibrio cells at the single-cell level under a homogeneous condition using this high-throughput system to repellent. In this colloquium, we would like to discuss these quantitative results.