Due to their structural complexity, biofilms exhibit highly heterogeneous internal microenvironments shaped by gradients of nutrients, metabolic products and signalling compounds. Here, bacterial cells essentially adjust their physiology according to the local conditions, which ultimately causes the stratification of the biofilms into physiologically distinct regions. Our work suggests that this physiological stratification not only represents a division of labor, where cell subpopulations locally specialize in fulfilling specific tasks, such as for example the production of extracellular matrix, but it also endows cell subpopulations with different capacities to cope with stresses as it is the case of antibiotic treatments. Our group is interested in characterizing this physiological stratification in biofilms of commensal and pathogenic E. coli strains and in understanding how this physiological heterogeneity influences the chances of cells to survive antibiotic treatments depending on their location within the biofilm. In particular, we seek to clarify how heterogeneity in the production of extracellular matrix components (amyloid curli and pEtN-cellulose), in stress responses, and in metabolism/growth among cell subpopulations influence antibiotic tolerance in E. coli biofilms. Knowledge of these aspects is crucial to design therapies that can target all cell subpopulations that coexist within these communities, irrespective of their physiological state and spatial location.