Figure 5.

Theoretical predictions for the band profiles for the full model (left) and gas kinetic models (23) (right) in the same range probed in experiments: C = 0.15–0.35%, as indicated. The population density B is plotted against colony radius R for advanced times T (quantities are dimensionless, see Methods). In the full model, as concentration is increased, the dynamics changes from chemotactic (sharp bands) to growth/diffusion-dominated (broad bands). This gradual transition is qualitatively the same as observed in experiment (see Fig. 1), and is not predicted by the gas kinetic model.