Evolutionary game theory of sticky motile bacteria

Bacteria typically reside in heterogeneous environments with varying nutrition and toxin profiles. Motile cells can gain an advantage over non-motile cells by migrating to more favorable environments. Since motility is energetically costly, cells must optimize their swimming speed and behavior to maximize their fitness. Here we look at how cheating strategies might evolve where slow or non-motile microbes exploit faster ones by sticking together and "hitching a ride."' We theoretically and computationally study the effects of sticking on the evolution of run speed in a controlled chemostat environment. We find stickiness allows slow cheaters to dominate only at intermediate distance between nutrition sources. In contrast, for long run durations slow microbes do gain a small advantage from sticking, but only get so far before falling behind; and for short run durations it is best for no one to swim.