Volume 109, Number 2, January 2015
|Number of page(s)||6|
|Section||Interdisciplinary Physics and Related Areas of Science and Technology|
|Published online||04 February 2015|
Random walk patterns of a soil bacterium in open and confined environments
1 University of Potsdam, Institute of Physics and Astronomy - Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
2 Technical University of Berlin, Institute of Theoretical Physics - Hardenbergstr. 36, 10623 Berlin, Germany
3 Max Planck Institute for the Physics of Complex Systems - Nöthnitzer Str. 38, 01187 Dresden, Germany
Received: 6 August 2014
Accepted: 14 January 2015
We used microfluidic tools and high-speed time-lapse microscopy to record trajectories of the soil bacterium Pseudomonas putida in a confined environment with cells swimming in close proximity to a glass-liquid interface. While the general swimming pattern is preserved, when compared to swimming in the bulk fluid, our results show that cells in the presence of two solid boundaries display more frequent reversals in swimming direction and swim faster. Additionally, we observe that run segments are no longer straight and that cells swim on circular trajectories, which can be attributed to the hydrodynamic wall effect. Using the experimentally observed parameters together with a recently presented analytic model for a run-reverse random walker, we obtained additional insight on how the spreading behavior of a cell population is affected under confinement. While on short time scales, the mean square displacement of confined swimmers grows faster as compared to the bulk fluid case, our model predicts that for large times the situation reverses due to the strong increase in effective rotational diffusion.
PACS: 87.17.Jj – Cell locomotion, chemotaxis / 87.16.Qp – Pseudopods, lamellipods, cilia, and flagella / 05.10.Gg – Stochastic analysis methods (Fokker-Planck, Langevin, etc.)
© EPLA, 2015
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