title: Collapsing bacterial cylinders.
abstract: Under special conditions bacteria excrete an attractant and aggregate. The high density regions initially collapse into cylindrical structures, which subsequently destabilize and break up into spherical aggregates. This paper presents a theoretical description of the process, from the structure of the collapsing cylinder to the spacing of the final aggregates. We show that cylindrical collapse involves a delicate balance in which bacterial attraction and diffusion nearly cancel, leading to corrections to the collapse laws expected from dimensional analysis. The instability of a collapsing cylinder is composed of two distinct stages: Initially, slow modulations to the cylinder develop, which correspond to a variation of the collapse time along the cylinder axis. Ultimately, one point on the cylinder pinches off. At this final stage of the instability, a front propagates from the pinch into the remainder of the cylinder. The spacing of the resulting spherical aggregates is determined by the front propagation.
authors.affiliation: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Betterton
authors.forename: M P
authors.initials: MP
authors.lastname: Brenner
mesh_terms: D018407:Bacterial Physiological Phenomena; D002633:Chemotaxis; D004926:Escherichia coli / Q000502:physiology*; D015233:Models, Statistical; D008962:Models, Theoretical; D013816:Thermodynamics; D013997:Time Factors