Modeling Light-Dependent Biofilm Morphology

Bacterial aggregates on submerged substrates can produce complex biofilm morphologies that are subject to environmental and metabolic factors. We develop a reductionistic cellular automata model of these structures with the intent of guiding experimentation and explaining prior results. We focus on reproducing the columnar and ``mushroom'' phases of aerobic \emph{R. palustris} and light-sensitive anaerobic \emph{R. palustris}, respectively. This light sensitivity requires the novel inclusion of a characteristic light penetration depth in addition to surface tension and media penetration parameters. We quantitatively divide this parameter space into roughly four morphological phases---columnar, mushroom, uniform, and irregular---by examining the resultant convexity defect distribution, horizontal correlation, and coverage as a function of height. Finally, we both validate experimental evidence of these phases and suggest new parameter regimes to investigate empirically.