  The dynamics of cellular aggregates is driven by the interplay of
mechanochemical processes and cellular activity. Although deterministic models
may capture mechanical features, local chemical fluctuations trigger random
cell responses, which determine the overall evolution. Incorporating stochastic
cellular behavior in macroscopic models of biological media is a challenging
task. Herein, we propose hybrid models for bacterial biofilm growth, which
couple a two phase solid/fluid mixture description of mechanical and chemical
fields with a dynamic energy budget-based cellular automata treatment of
bacterial activity. Thin film and plate approximations for the relevant
interfaces allow us to obtain numerical solutions exhibiting behaviors observed
in experiments, such as accelerated spread due to water intake from the
environment, wrinkle formation, undulated contour development, and the
appearance of inhomogeneous distributions of differentiated bacteria performing
varied tasks.
