title: An Element of Determinism in a Stochastic Flagellar Motor Switch.
abstract: Marine bacterium Vibrio alginolyticus uses a single polar flagellum to navigate in an aqueous environment. Similar to Escherichia coli cells, the polar flagellar motor has two states; when the motor is counter-clockwise, the cell swims forward and when the motor is clockwise, the cell swims backward. V. alginolyticus also incorporates a direction randomization step at the start of the forward swimming interval by flicking its flagellum. To gain an understanding on how the polar flagellar motor switch is regulated, distributions of the forward Δf and backward Δb intervals are investigated herein. We found that the steady-state probability density functions, P(Δf) and P(Δb), of freely swimming bacteria are strongly peaked at a finite time, suggesting that the motor switch is not Poissonian. The short-time inhibition is sufficiently strong and long lasting, i.e., several hundred milliseconds for both intervals, which is readily observed and characterized. Treating motor reversal dynamics as a first-passage problem, which results from conformation fluctuations of the motor switch, we calculated P(Δf) and P(Δb) and found good agreement with the measurements.
authors.affiliation: Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, United States of America.
authors.forename: Li
authors.initials: L
authors.lastname: Xie
authors.affiliation: Department of Physics, Simon Fraser University, Burnaby, BC, Canada.
authors.forename: Tuba
authors.initials: T
authors.lastname: Altindal
authors.affiliation: Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, United States of America.
authors.forename: Xiao-Lun
authors.initials: XL
authors.lastname: Wu
mesh_terms: D002633:Chemotaxis / Q000502:physiology; D005407:Flagella / Q000502:physiology*; D020409:Molecular Motor Proteins / Q000502:physiology*; D016012:Poisson Distribution; D013269:Stochastic Processes; D044149:Vibrio alginolyticus / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D020409:Molecular Motor Proteins