In this talk I will put forward some ideas about how different bacterial motility patterns can be regulated, allowing bacteria to perform chemotaxis efficiently in different environments. Some of these ideas are motivated by our recent observations of a marine bacterium that possesses a single polar flagellum, which enables the bacterium to backtrack as well as to randomize its swimming directions. Using video imaging and optical trapping, we found that the flagella motor of this bacterium is not regulated by a Poissonian process, which is at variance with that of E. coli. Specifically, we found that in the marine bacterium the nascent rotation state is protected for a short period of time, 0.2-0.3 s, before the motor can be switched again. The enforcement of the current state requires a toggle switch-like logic, which we posit to be beneficial for bacterial chemotaxis in an aquatic environment where chemical signals appear and disappear rapidly due to turbulence dispersion on small spatial scales.
The PI is a condensed matter physicist who has a broad interest in science. His earlier research was in soft condensed matter physics and fluid turbulence. Using freely suspended fluid films, which behaved like a two-dimensional fluid medium, he investigated turbulence fluctuations in low spatial dimensions. During the course of this study, he found novel applications of the film for growing 2D crystals and for studying collective motions of swimming bacteria. He also studied non-equilibrium statistical physics of polymer solutions and liquid crystals. His current research interest is in biophysics. The works in this area include the study of stochastic gene expression and its effect on coexistence of bacterium and phage, and bacterial swimming and chemotaxis.
Ph.D., Cornell University, 1987
Postdoc., Exxon Research and Engineering Co., 1987-1989
Postdoc., Princeton University, 1989-1990
Assistant Prof., University of Pittsburgh, 1990-1996
Associate Prof., University of Pittsburgh, 1996-2003
Professor, University of Pittsburgh, 2003-present
Awards: Distinguished lecturer of Sigma-Xi Society, 1999-2000.
Five Relevant Publications:
(1) Flagellum and Rudder Are One; New Modes of Bacterial Swimming and Chemotaxis, Li Xie, Tuba Altindal, Suddhashil Chattopadhyay, and X.L. Wu, PNAS, 108 2246 (2011)
(2) Bacterial chemotaxis in an optical trap, Tuba Altindal, Suddhashil Chattopadhyay, and X.L. Wu, ProS One, 6 e182331 (2011)
(3) Implications of 3-step swimming patterns in bacterial chemotaxis, Tuba Altindal, Li Xie, and X.L. Wu, Biophysical Journal, 100 32 (2011)
(4) The effect of long-range hydrodynamic interaction on the swimming of a single bacterium, S. Chattopadhyay and X.L. Wu, Biophys. J., 96 2023 (2009).(5) Stochastic Receptor Expression Allows Sensitive Bacteria to Evade Phage Attack. Part I: Experiments, E. Chapman-McQuiston and X.L. Wu, Biophys. J., 94, 4537-4548 (2008); and Part II: Theoretical Analyses, E. Chapman-McQuiston and X.L. Wu, Biophys. J., 94, 4525 (2008)
Five Other Publications
(1) On Kinetics of Phage Adsorption, R. Moldovan, E. Chapman-McQuiston, X.L. Wu, Biophys. J., 93, 303 (2007).
(2) Swimming Efficiency of Bacterium Escherichia Coli, S. Chattopadhyay, R. Moldovan, C. Yeung, and X.L. Wu, Proc. Nat. Acad. Sci. 103, 13712 (2006)
(3) Stick-and-Diffuse and Caged Diffusion: a Comparison of Two Models of Synaptic Vesicle Dynamics, C. Yeung, M. Shtrahman, and X.L. Wu, Biophys. J. 92, 2271 (2007).
(4) Vesicle Dynamics in Single Hippocampal Synapses Probed, M. Shtrahman, C. Yeung, D.W. Nauen, G.Q. Bi, and X.L. Wu, Biophys. J. 89, 3615 (2005).
(5) Polymer Effects on Small- and Large-scale Two-dimensional Turbulence, Y.G. Jun and X.L. Wu, Phys. Rev. Lett. 96, 024502 (2006).