Patterns of the morpho-phenotypic expression in wrinkled biofilms

Phenotypic heterogeneity in biofilms enhances fitness through mechanism such as bet-hedging, division of labor, and metabolic diversity. In particular, the coexistence of phenotypes capable of secreting extracellular polymeric substances that constitute the extracellular matrix plays a key role in shaping the complex wrinkled morphologies of mature biofilms. These morphologies have been linked to collective advantages such as improved nutrient access, and increased resistance to environmental stresses. Despite its importance, the feedback between phenotypic expression and morphological evolution in biofilms remains poorly understood. To address this challenge, we developed a model that couples morphological evolution and phenotypic organization during biofilm growth. The model distinguishes three governing mechanisms of phenotypic expression: (1) environmental response, involving phenotype switching driven by local nutrient fields; (2) environmental selection, in which differential growth of matrix-producing and motile cells determines population composition, and (3) stochastic bistable switching, noise-driven transitions between phenotypes. Determining which mechanism dominates under specific conditions is essential for understanding how biofilms adapt their form and function. Model predictions are analyzed in the context of E. coli and B. subtilis biofilms, revealing how phenotypic heterogeneity and structural complexity co-emerge to enhance biofilm fitness.