%0 Journal Article
%T Arrested phase separation in reproducing bacteria: a generic route to pattern formation?
%A M. E. Cates
%A D. Marenduzzo
%A I. Pagonabarraga
%A J. Tailleur
%J Quantitative Biology
%D 2010
%I arXiv
%R 10.1073/pnas.1001994107
%X We present a generic mechanism by which reproducing microorganisms, with a diffusivity that depends on the local population density, can form stable patterns. It is known that a decrease of swimming speed with density can promote separation into bulk phases of two coexisting densities; this is opposed by the logistic law for birth and death which allows only a single uniform density to be stable. The result of this contest is an arrested nonequilibrium phase separation in which dense droplets or rings become separated by less dense regions, with a characteristic steady-state length scale. Cell division mainly occurs in the dilute regions and cell death in the dense ones, with a continuous flux between these sustained by the diffusivity gradient. We formulate a mathematical model of this in a case involving run-and-tumble bacteria, and make connections with a wider class of mechanisms for density-dependent motility. No chemotaxis is assumed in the model, yet it predicts the formation of patterns strikingly similar to those believed to result from chemotactic behavior.
%U http://arxiv.org/abs/1001.0057v1