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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