Biofilm formation is a hallmark of prokaryotic lifestyle and is characterized by strong regulation and out-differentiation of subpopulations with distinct properties. During maturation, embedded cells experience a vast array of mechanical, chemical and potential forces, which govern the structure of the emergent biofilm and predict dynamical expansion due to proliferation. These interactions cross multiple length and time scales and are in general emergent, i.e. absent for planktonic cells. For the human pathogen Neisseria gonorrhoeae, aggregation is initiated by the action of Type 4 Pili, thin protruding cell appendages that allow dynamic surface and cell-to-cell binding. We investigate different steps in the maturation of gonococcal colonies and highlight physical mechanisms that decide the fate of proliferating cell aggregates. Most prominently, we emphasize the importance of cellular membrane potential as a collective out-differentiation trigger and stress the impact of heterogeneities on antibiotic susceptibility.