Bacterial adhesion on surfaces is a very important complex phenomenon, since it is a determinant for the overall biofilm formation; the presence of biofilm can be both beneficial (i.e. to degrade hazardous substances in the soil or in a bioreactor) or detrimental (as on food, ship hulls and biomaterials implants or in the oral cavity). This work starts from a series of experiments carried out on different engineered surfaces on which bacteria adhere in such a way a pattern emerges. In this paper a model based on self-organization and thus ruled by local laws among the elements of the complex system is introduced. It is shown how this model accounts for generation of the patterns in bacterial adhesion.