Schedule Jan 14, 2016
Range expansions in structured environments
David Nelson, Harvard & KITP

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 experiments carried out by Wolfram Moebius, 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 non-equilibrium 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.

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