A Bacterial Swimmer with Two Alternating Speeds of Propagation |
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| Authors: | Matthias Theves Johannes Taktikos Vasily Zaburdaev Holger Stark Carsten Beta |
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| Institution: | †Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany;‡Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany;§Institut für Theoretische Physik, Technische Universität Berlin, Berlin, Germany |
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| 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. |
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