Table 1. Set of parameters.

Time scale		Experimental evidence
Space scale		Experimental evidence
Effective bacterial diffusion		[47]
Chemical diffusion		[4]
Chemical degradation		[25] and experimental fit
Effective bacterial chemotaxis speed		Experimental fit
Effective bacterial chemotaxis speed		Experimental fit
*Response function*	step or
*Total number of cells*		Experimental measurement
*Chemical secretion*		[25]
*Nutrient diffusion*
*Nutrient consumption*		[25]

Reference set of parameters which have been used in the numerical simulations. The asterisks point out the parameters which have little influence on the dynamics: they have been chosen in agreement with the other parameters (with respect to the order of magnitude). The three parameters , and have been obtained from the macroscopic observables , and using the formulas (7), (8): , , . We obtain a value for which is consistent with [25]. See Materials and Methods for details.