title: A bacterial swimmer with two alternating speeds of propagation.
abstract: We recorded large data sets of swimming trajectories of the soil bacterium Pseudomonas putida. Like other prokaryotic swimmers, P. putida exhibits a motion pattern dominated by persistent runs that are interrupted by turning events. An in-depth analysis of their swimming trajectories revealed that the majority of the turning events is characterized by an angle of ϕ1 = 180° (reversals). To a lesser extent, turning angles of ϕ2 = 0° are also found. Remarkably, we observed that, upon a reversal, the swimming speed changes by a factor of two on average-a prominent feature of the motion pattern that, to our knowledge, has not been reported before. A theoretical model, based on the experimental values for the average run time and the rotational diffusion, recovers the mean-square displacement of P. putida if the two distinct swimming speeds are taken into account. Compared to a swimmer that moves with a constant intermediate speed, the mean-square displacement is strongly enhanced. We furthermore observed a negative dip in the directional autocorrelation at intermediate times, a feature that is only recovered in an extended model, where the nonexponential shape of the run-time distribution is taken into account.
authors.affiliation: Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Theves
authors.forename: Johannes
authors.initials: J
authors.lastname: Taktikos
authors.forename: Vasily
authors.initials: V
authors.lastname: Zaburdaev
authors.forename: Holger
authors.initials: H
authors.lastname: Stark
authors.forename: Carsten
authors.initials: C
authors.lastname: Beta
mesh_terms: D008954:Models, Biological; D009068:Movement; D016958:Pseudomonas putida / Q000502:physiology*; D013997:Time Factors