Dr. BAi, Fan (白凡)

Assistant Professor, Biodynamic Optical Imaging Center, Peking University

Abstract: The switch that controls the direction of flagellar rotation during bacterial chemotaxis has a highly cooperative response. This has previously been understood in terms of the classic two-state, concerted model of allosteric regulation.Here, we used high-resolution optical microscopy to observe switching of single motors and uncover the stochastic multistate nature of the switch. Our observations are in detailed quantitative agreement with a recent general model of allosteric cooperativity that exhibits conformational spread, namely the stochastic growth and shrinkage of domains formed by neighboring subunits sharing a particular conformational state.By incorporating a torque-dependent flipping rate, we extended the conformational spread model to explain the latest experimental observation: flagellar motor switch responds to external load as well as chemotactic signal.

Our recent experiment observed a large group of single E. coli flagellar motors switching in the physiological regime. We showed that motor switching has stable individuality. Two properties of motor switching the switching bias and mean switching duration vary significantly from cell to cell. We propose such individuality may allow populations of cells to better survive in rapidly changing environments by “hedging their bets”.

 Date & Time: February 16, 2012（Thursday）   14:30 – 16:30
 Location: 606 Conference Room