Biofilm formation in confined environments

Biofilms are microbial communities that develop when free-swimming (planktonic) bacteria transition to a non-motile, surface-attached state, sharing similarities with motility-induced phase separation. This transition is modulated by environmental factors such as nutrient availability, chemical and mechanical stresses, as well as collective response of bacteria through quorom sensing. Despite the inherent heterogeneity in their natural environments, biofilm formation has often been studied in unconfined settings. Here, using microfluidic experiments, we study the influence of confinement on the spatiotemporal evolution of biofilm formation and growth. Our observations and theoretical modeling demonstrate that the interplay between bacterial growth and self-generated nutrient gradients can modulate the spatial patterning of biofilms in confinement, pointing to the importance of geometric effects on biofilm formation and growth in heterogeneous environments.