R eaction-di usion m odelfor pattern form ation in E : coli sw arm ing colonies w ith slim e

A new experim entalcolonialpattern and pattern transition observed in E :coliM G 1655 swarm ing cells grown on sem i-solid agar are described. W e present a reaction-di usion m odelthat,taking into accounttheslim e generated by thesecellsand itsin uenceon thebacterialdi erentiation and m otion,reproducesthepattern and successfully predictstheobserved changeswhen thecolonialcollectivem otility islim ited.In spite ofhaving sm allnon-hyper agellated swarm ing cells,underthese experim entalconditionsE.coliM G 1655 can very rapidly colonize a surface,with a low branching rate,thanksto a strong uid production and a localincrem ented density ofm otile,lubricating cells.