  Many species of microbes cooperate by producing public goods from which they
collectively benefit. However, these populations are under the risk of being
taken over by cheating mutants that do not contribute to the pool of public
goods. Here we present theoretical findings that address how the social
evolution of microbes can be manipulated by external perturbations, to inhibit
or promote the fixation of cheaters. To control social evolution, we determine
the effects of fluid-dynamical properties such as flow rate or boundary
geometry. We also study the social evolutionary consequences of introducing
beneficial or harmful chemicals at steady state and in a time dependent
fashion. We show that by modulating the flow rate and by applying pulsed
chemical signals, we can modulate the spatial structure and dynamics of the
population, in a way that can select for more or less cooperative microbial
populations.
