Biological organisms in the real world do not typically grow up in well-mixed test tubes or featureless Petri dishes, but instead must find ways to prosper in the presence of environmental inhomogeneities that vary in space. In a collaboration with Wolfram Moebius and Andrew Murray, we have created a spatially random bacterial lawn on a Petri dish, with two fluorescently labelled E. coli strains, one which is highly susceptible to phage T7, and one which is not. Dark viral plaques due to T7 infect and expand through a mottled environment, sometimes tunneling through barriers provided by the less susceptible species. We have also developed the capability to print bacterial lawns in prescribed patterns. Such experiments, when combined with a theory of the nonequilibrium statistical dynamics of viral diffusion, mutation, genetic drift and selective advantage, have considerable potential for understanding the spread of viral epidemics, the effect of spatial bottlenecks on evolution, etc. By probing multicolored bacterial range expansions around nutrient-free obstacles, we also study the effect of spatial inhomogeneities on genetic demixing.
Lunch @ 11:45, seminar begins at 12 noon.