New Features of Chemotactic Behavior in a Marine Bacterium

Abstract

Using optical trapping we investigated chemotactic response of marine bacterium Vibrio alginolyticus to a brief stimulation by serine. Although this bacterial strain possesses only a single polar flagellum and its motility pattern is different from that of enteric bacteria, such as Escherichia coli (E. coli), the chemotactic response appears suprisingly similar, i.e. both are biphasic. However, in details, the two response functions are different in that the relevant time scales, the short activation and the long adaption times, are shorter in V. alginolyticus than in E. coli, reflecting perhaps different ecosystems these bacteria live. In addition to the overall biphasic response, the response function appears to have fine structures that are sensitive to the exposure time αt of the cell to serine, i.e., the amplitude of the fine structures increases with αt and reaches a maximum in about 1.5 s, and then the amplitude decreases with longer αt. We also investigated V. alginolyticus response to different serine concentrations. Such measurements allow us to conclude that this marine strain is at least a factor of ten more sensitive to low concentration of serine than E. coli. It remains a challenge in future studies to understand how the above measured attributes allow the cells of V. alginolyticus to thrive in an ocean environment.