A diffusion-reaction model for the growth of bacterial colonies is presented. The often observed cooperative
behavior developed by bacteria which increases their motility in adverse growth conditions is here introduced
as a nonlinear diffusion term. The presence of this mechanism depends on a response which can present
hysteresis. By changing only the concentrations of agar and initial nutrient, numerical integration of the
proposed model reproduces the different patterns shown by Bacillus subtilis OG-01.Peer Reviewe