Physical Sensing of Surface Properties by Microswimmers--Directing Bacterial Motion via Wall Slip.

Jinglei Hu,Roland G Winkler,Gerhard Gompper,Adam Wysocki

doi:10.1038/srep09586

Abstract

Bacteria such as Escherichia coli swim along circular trajectories adjacent to surfaces. Thereby, the orientation (clockwise, counterclockwise) and the curvature depend on the surface properties. We employ mesoscale hydrodynamic simulations of a mechano-elastic model of E. coli, with a spherocylindrical body propelled by a bundle of rotating helical flagella, to study quantitatively the curvature of the appearing circular trajectories. We demonstrate that the cell is sensitive to nanoscale changes in the surface slip length. The results are employed to propose a novel approach to directing bacterial motion on striped surfaces with different slip lengths, which implies a transformation of the circular motion into a snaking motion along the stripe boundaries. The feasibility of this approach is demonstrated by a simulation of active Brownian rods, which also reveals a dependence of directional motion on the stripe width.

Highlights

Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Julich, D-52425 Julich, Germany
The results are employed to propose a novel approach to directing bacterial motion on striped surfaces with different slip lengths, which implies a transformation of the circular motion into a snaking motion along the stripe boundaries
The swimming behavior of bacteria near surfaces is governed by hydrodynamic forces[6,7] and, the CW and CCW circular trajectories of E. coli have been explained in terms of hydrodynamic interactions.[2,3]

Summary

Introduction

A trajectory can be expected to switch from CW to CCW (or vice versa) when b reaches some characteristic value b0 Such a transition has been observed experimentally for E. coli swimming near glass surfaces upon addition of alginate, and has been attributed to changes in the slip length.[11] An attempt of a unified description has been presented, based on the far-field approximation of hydrodynamic interactions.[12] Yet, there is no quantitative theoretical or simulation study on the effect of slip on the swimming behavior of bacteria at surfaces. The obtained dependence of the curvature on the slip length is well described by a simple derived theoretical expression We employ these insights to suggest a novel route to direct bacterial motion www.nature.com/scientificreports by patterning a surface with stripes of different slip lengths and corresponding CW and CCW trajectories, respectively. We demonstrate the viability of this approach by a simulation of active Brownian rods, and elucidate the dependence of the diffusion anisotropy on the stripe width

Methods

Results

Conclusion