Volume 86, Number 6, June 2009
Article Number 60002
Number of page(s) 6
Section General
Published online 30 June 2009
EPL, 86 (2009) 60002
DOI: 10.1209/0295-5075/86/60002

Sedimentation, trapping, and rectification of dilute bacteria

J. Tailleur and M. E. Cates

SUPA, School of Physics And Astronomy - University of Edinburgh - JCMB Kings Buildings, Edinburgh EH9 3JZ, UK, EU

received 27 March 2009; accepted in final form 26 May 2009; published June 2009
published online 30 June 2009

The run-and-tumble dynamics of bacteria, as exhibited by E. coli, offers a simple experimental realization of non-Brownian, yet diffusive, particles. Here we present some analytic and numerical results for models of the ideal (low-density) limit in which the particles have no hydrodynamic or other interactions and hence undergo independent motions. We address three cases: sedimentation under gravity; confinement by a harmonic external potential; and rectification by a strip of “funnel gates" which we model by a zone in which tumble rate depends on swim direction. We compare our results with recent experimental and simulation literature and highlight similarities and differences with the diffusive motion of colloidal particles.

05.40.-a - Fluctuation phenomena, random processes, noise, and Brownian motion.
87.10.Mn - Stochastic modeling.
87.17.Jj - Cell locomotion, chemotaxis.

© EPLA 2009