PhD Defense: Yang Yang

April 27, 2018

Title: BACTERIAL MOTILITY PATTERNS IN CHEMOTAXIS AND POLYMER SOLUTIONS


Abstract: We investigate bacterial chemotactic strategies usingrun-tumble and run-reverse-flick motility patterns. The former is typicallyobserved in enteric bacteria such as Escherichia coli and Salmonella, and thelatter is observed in marine bacteria Vibrio alginolyticus and possiblyexhibited by other polar flagellated species. It is shown that while the 3-stepmotility pattern helps the bacterium to localize near hot spots, anexploitative behavior, its exploratory potential in short times can besignificantly enhanced by employing a non-Poissonian regulation scheme for itsflagellar motor switches.

 

 

We also explored the interaction of polymer solutions withVibrio alginolyticus. As the polymer concentrations increase, the flick of Vibrioalginolyticus is suppressed by the surrounding media. Two theoretic models aredeveloped to explain the interaction, which confirms non-Poissonian property ofVibrio alginolyticus swimming interval distribution and reveals that motorfluctuations can be modeled with a damped harmonic oscillator. The motorfluctuations are coupled with the viscoelastic environment so that aresonance-like effect can be observed. On the other hand, we only see thedecreasing of swimming speed with increasing polymer concentration, which isdifferent 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.

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219 Allen Hall