BACTERIAL MOTILITY PATTERNS IN CHEMOTAXIS AND POLYMER SOLUTIONS

We investigate bacterial chemotactic strategies using run-tumble and run-reverse-flick motility patterns. The former is typically observed in enteric bacteria such as Escherichia coli and Salmonella, and the latter is observed in marine bacteria Vibrio alginolyticus and possibly exhibited by other polar flagellated species. It is shown that while the 3-step motility pattern helps the bacterium to localize near hot spots, an exploitative behavior, its exploratory potential in short times can be significantly enhanced by employing a non-Poissonian regulation scheme for its flagellar motor switches. We also explored the interaction of polymer solutions with Vibrio alginolyticus. As the polymer concentrations increase, the flick of Vibrio alginolyticus is suppressed by the surrounding media. Two theoretical models are developed to explain the interaction, which confirms non-Poissonian property of Vibrio alginolyticus swimming interval distribution and reveals that motor fluctuations can be modeled with a damped harmonic oscillator. The motor fluctuations are coupled with the viscoelastic environment so that a “resonance-like” effect of the directional autocorrelation function of swimming bacteria can be observed. On the other hand, we only see the decreasing of swimming speed with increasing polymer concentration, which is different from the non-monotonic results of E. coli observed by Martinez et al. The swimming speed vs. concentration of polymer solutions shows a scaling law