IMI Interdisciplinary Mathematics InstituteCollege of Arts and Sciences

Multiscale Modeling in Biology

  • April 16, 2012
  • 3:30 p.m.
  • LeConte 412

Abstract

Many bacteria can rapidly traverse surfaces from which they are extracting nutrient for growth by generating flat, spreading colonies, called swarms because they resemble swarms of insects. M. xanthus, a common soil bacteria that is studied in part for the high level of social coordination, regularly reverse direction of their motion and organize into single layers of small clusters and large rafts of cells at the edge of a spreading swarms. Coupled multiscale model simulations and experimental bacteria tracking will be used in this talk to demonstrate how the flexibility and adhesion between cells as well as cell reversals result in bacteria effectively colonizing surfaces [1, 2]. A connection will be also described between a microscopic one-dimensional stochastic model of reversing non overlapping bacteria and a macroscopic nonlinear diffusion equation describing the dynamics of cellular density [3].

In the second half of the talk, P. aeruginosa, main infection in hospitals, will be shown to propagate as high density waves that move symmetrically as rings within swarms towards the extending tendrils. Biologically-justified cell-based multiscale model simulations suggest a mechanism of wave propagation as well as branched tendril formation at the edge of the population that depend upon competition between the changing viscosity of the bacterial liquid suspension and the liquid film boundary expansion caused by Marangoni forces [4]. Therefore, P. aeruginosa efficiently colonizes surfaces by controlling the physical forces responsible for expansion of thin liquid films and by propagating towards the tendril tips. The model predictions of wave speed and swarm expansion rate as well as cell alignment in tendrils were confirmed experimentally.

  1. C.W. Harvey, F. Morcos, C.R. Sweet, D. Kaiser, S. Chatterjee, X. Lu, D. Chen and M. Alber [2011], Study of elastic collisions of M. xanthus in swarms, Physical Biology 8, 026016.

  2. Y. Wu, Y. Jiang, D. Kaiser and M. Alber [2009], Periodic reversal of direction allows Myxobacteria to swarm, Proc. Natl. Acad. Sci. USA 106 4 1222-1227 (featured in the Nature News, January 20th, 2009, doi:10.1038/news.2009.43).

  3. R. Gejji, P. Lushnikov and M. Alber [2012], Macroscopic model of self-propelled bacteria swarming with regular reversals, Physical Review E 85, 021903.

  4. H. Du, Z. Xu, J.D. Shrout and M. Alber [2011], Multiscale Modeling of Pseudomonas aeruginosa Swarming, Mathematical Models and Methods in Applied Sciences, Vol. 21,Suppl. 939-954.

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