Reaction-diffusion model for pattern formation in E. coli swarming colonies with slime

A new experimental colonial pattern and pattern transition observed in E. coli MG1655 swarming cells grown on semi-solid agar are described. We present a reaction-diffusion model that, taking into account the slime generated by these cells and its influence on the bacterial differentiation and motion, reproduces the pattern and successfully predicts the observed changes when the colonial collective motility is limited. In spite of having small non-hyperflagellated swarming cells, under these experimental conditions E. coli MG1655 can very rapidly colonize a surface, with a low branching rate, thanks to a strong fluid production and a local incremented density of motile, lubricating cells.