title: From the Cover: Bacterial flagellum as a propeller and as a rudder for efficient chemotaxis.
abstract: We investigate swimming and chemotactic behaviors of the polarly flagellated marine bacteria Vibrio alginolyticus in an aqueous medium. Our observations show that V. alginolyticus execute a cyclic, three-step (forward, reverse, and flick) swimming pattern that is distinctively different from the run-tumble pattern adopted by Escherichia coli. Specifically, the bacterium backtracks its forward swimming path when the motor reverses. However, upon resuming forward swimming, the flagellum flicks and a new swimming direction is selected at random. In a chemically homogeneous medium (no attractant or repellent), the consecutive forward t(f) and backward t(b) swimming times are uncorrelated. Interestingly, although t(f) and t(b) are not distributed in a Poissonian fashion, their difference Δt = |t(f) - t(b)| is. Near a point source of attractant, on the other hand, t(f) and t(b) are found to be strongly correlated, and Δt obeys a bimodal distribution. These observations indicate that V. alginolyticus exploit the time-reversal symmetry of forward and backward swimming by using the time difference to regulate their chemotactic behavior. By adopting the three-step cycle, cells of V. alginolyticus are able to quickly respond to a chemical gradient as well as to localize near a point source of attractant.
authors.affiliation: Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Xie
authors.forename: Tuba
authors.initials: T
authors.lastname: Altindal
authors.forename: Suddhashil
authors.initials: S
authors.lastname: Chattopadhyay
authors.forename: Xiao-Lun
authors.initials: XL
authors.lastname: Wu
mesh_terms: D002633:Chemotaxis / Q000502:physiology*; D004926:Escherichia coli / Q000502:physiology*; D005408:Flagellin / Q000378:metabolism*; D044149:Vibrio alginolyticus / Q000502:physiology*
chemical_list: D005408:Flagellin