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Directed collective motion of bacteria under channel confinement

Published version
Peer-reviewed

Type

Article

Change log

Authors

Wioland, H 
Lushi, E 
Goldstein, RE 

Abstract

Dense suspensions of swimming bacteria are known to exhibit collective behaviour arising from the interplay of steric and hydrodynamic interactions. Unconfined suspensions exhibit transient, recurring vortices and jets, whereas those confined in circular domains may exhibit order in the form of a spiral vortex. Here we show that confinement into a long and narrow macroscopic ‘racetrack’ geometry stabilises bacterial motion to form a steady unidirectional circulation. This motion is reproduced in simulations of discrete swimmers that reveal the crucial role that bacteria-driven fluid flows play in the dynamics. In particular, cells close to the channel wall produce strong flows which advect cells in the bulk against their swimming direction.Weexamine in detail the transition from a disordered state to persistent directed motion as a function of the channel width, and show that the width at the crossover point is comparable to the typical correlation length of swirls seen in the unbounded system. Our results shed light on the mechanisms driving the collective behaviour of bacteria and other active matter systems, and stress the importance of the ubiquitous boundaries found in natural habitats.

Description

Keywords

bacteria, confinement, collective behaviour

Journal Title

New Journal of Physics

Conference Name

Journal ISSN

1367-2630
1367-2630

Volume Title

18

Publisher

IOP Publishing
Sponsorship
European Research Council (247333)