title: Barrier Crossing in Escherichia coli Chemotaxis.
abstract: We study cell navigation in spatiotemporally complex environments by developing a microfluidic racetrack device that creates a traveling wave with multiple peaks and a tunable wave speed. We find that while the population-averaged chemotaxis drift speed increases with wave speed for low wave speed, it decreases sharply for high wave speed. This reversed dependence of population-averaged chemotaxis drift speed on wave speed is caused by a "barrier-crossing" phenomenon, where a cell hops backwards from one peak attractant location to the peak behind by crossing an unfavorable (barrier) region with low attractant concentrations. By using a coarse-grained model of chemotaxis, we map bacterial motility in an attractant field to the random motion of an overdamped particle in an effective potential. The observed barrier-crossing phenomenon of living cells and its dependence on the spatiotemporal profile of attractant concentration are explained quantitatively by Kramers reaction rate theory.
authors.affiliation: Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
authors.forename: Zhaojun
authors.initials: Z
authors.lastname: Li
authors.affiliation: Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
authors.forename: Qiuxian
authors.initials: Q
authors.lastname: Cai
authors.affiliation: Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
authors.forename: Xuanqi
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
authors.forename: Guangwei
authors.initials: G
authors.lastname: Si
authors.affiliation: Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.|Center for Quantitative Biology, Peking-Tsinghua Center for Life Science, Peking University, Beijing 100871, China.|The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Ouyang
authors.affiliation: Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.|The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China.
authors.forename: Chunxiong
authors.initials: C
authors.lastname: Luo
authors.affiliation: Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.|IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors.forename: Yuhai
authors.initials: Y
authors.lastname: Tu
mesh_terms: D002633:Chemotaxis; D003198:Computer Simulation; D004926:Escherichia coli; D044085:Microfluidics; D008954:Models, Biological