Friday 16 Mar 2012Colloquium: Phase Separation and Pattern Formation in Motile Bacteria

Prof. Michael Cates (2009 IOP Dirac Medal) - University of Edinburgh

Newman F 12:00-13:00

Bacteria are of similar dimensions to inert colloidal particles, but exhibit at least two types of behaviour that colloids do not: motility (or self-propulsion) and the ability to reproduce. Both depend on the continuous supply of food and therefore violate the principle of microscopic reversibility (detailed balance) which strongly constrains the Brownian motion of ordinary colloids.

I will describe simple statistical-physics models of bacterial motion, whose generic consequences include (a) liquid-gas type phase separation among particles with no attractive forces, and (b) patterns created from a continuous competition between phase separation and reproduction. The latter offers a simple physical explanation for the patterns long seen experimentally in growing colonies of bacteria such as E. coli and S. typhimurium.

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