Stress and Alignment Response to Complex Confinement in Bacterial Monolayers*

Bacterial monolayers are precursors to biofilms, durable structures that enable bacteria to survive in otherwise harsh environments. Growing monolayers of rod-shaped cells act as an active nematic with a complex interplay of alignment and internal forces that has attracted significant interest and study. Previous research has made progress in describing the mechanics of cell alignment in unconstrained or simply confined environments. However, understanding the response of these colonies to more complex and dynamic environments is vital for predicting their behavior in real-world conditions. We present simulations of colonies subject to external perturbation such as obstacles within the colony and moving boundaries. Varying obstacle size and curvature and time-dependent boundary conditions, we characterize the monolayers’ stress and alignment response to these perturbations. Our findings allow us to better understand the link between alignment and internal force response to external disturbances in growing cell monolayers.