An individual-based model for biofilm formation at liquid surfaces

TL;DR

This paper presents an individual-based mathematical model for biofilm formation at liquid surfaces, incorporating bacterial phenotypes, chemotaxis, and fluid interactions, successfully reproducing experimental biofilm development stages.

Contribution

The model uniquely couples discrete bacterial behavior with environmental advection-diffusion, capturing biofilm formation dynamics and morphology influenced by phenotypic states and fluid flow.

Findings

Model reproduces laboratory biofilm formation stages

Bacterial phenotypes significantly affect biofilm morphology

Fluid advection and bioconvection influence biofilm development

Abstract

The bacterium {\em Bacilus subtilis} frequently forms biofilms at the interface between the culture medium and the air. We develop a mathematical model that couples a description of bacteria as individual discrete objects to the standard advection-diffusion equations for the environment. The model takes into account two different bacterial phenotypes. In the motile state, bacteria swim and perform a run-and-tumble motion that is biased toward regions of high oxygen concentration (aerotaxis). In the matrix-producer state they excrete extracellular polymers, which allows them to connect to other bacteria and to form a biofilm. Bacteria are also advected by the fluid, and can trigger bioconvection. Numerical simulations of the model reproduce all the stages of biofilm formation observed in laboratory experiments. Finally, we study the influence of various model parameters on the dynamics and morphology of biofilms.