Quantitative cellular automaton model for biofilms

A fully quantitative cellular automaton (CA) biofilm model was developed. T he model describes substrate and biomass as discrete particles existing and interacting in a specified physical domain. Substrate particles move by ra ndom walks, simulating molecular diffusion. Microbial particles grow attach ed to a surface or to other microbial particles, consume substrate particle s, and duplicate if a sufficient amount of substrate is consumed. The dynam ics of the system are simulated using stochastic processes that represent t he occurrence of specific events, such as substrate diffusion, substrate ut ilization, biofilm growth, and biofilm decay and detachment. The ability of the CA model to predict substrate gradients and fluxes was evaluated by co mparing model simulations to predictions from a traditional differential eq uations model. One and 2D CA models were evaluated. In general, CA model pr edictions of steady-state flux, biofilm thickness, and substrate gradients inside the biofilm fitted well the differential equations model results; th e 2D model had a better agreement at high substrate concentrations. Fully q uantitative CA biofilm models offer an alternative approach to simulate bio film activity and development. Specific advantages of CA modeling include t he ability to simulate growth of heterogeneous biofilms with irregular boun dary conditions, and the possibility of developing computationally efficien t parallel processing algorithms for the quantitative simulation of biofilm s in two and three dimensions.