Science / Technology - Colloquium
Monday, October 8, 2007
4:00 PM-5:00 PM
Olin Hall
107
Under appropriate conditions of wetness and temperature, many commonly studied bacteria form a thin, highly dynamic layer that quickly grows to cover an agar plate. This phenomenon, known as swarming, enables rapid colonization of a rich medium. Swarmer cells are phenotypically distinct from vegetative cells they are longer, more highly flagellated, and more motile and some of the genes that govern swarm differentiation have been identified.
The edge of a swarm colony is an extensive monolayer of billions of constantly moving cells. Formally, this should be described by the two-dimensional statistical mechanics of a self-propelled gas, sometimes known as 'boid' theory. Versions of this theory predict phase transitions and the emergence of long-range symmetry-breaking order. We are currently measuring the statistical properties of cell motion in Escherichia coli swarm monolayers, and comparing them to the better-known statistics of cell swimming in bulk (3D) fluid. To date, we have high-magnification data covering the motion of individual cells, but we have seen coherent motions over length scales of more than two orders of magnitude limited only by our ability to make large, homogeneous swarms. I will discuss our observed short-range anisotropic velocity correlation function as a combination of nematic liquid crystal order and self-propulsion.
Cost: FREE
Suggested Audiences: College
E-mail:
sak@wpi.edu
Phone: 508-831-5090
Last Modified: October 3, 2007 at 10:26 AM
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