Biofilm Growth Under Elastic Confinement

TL;DR

This study investigates biofilm growth in confined elastic environments, revealing a new growth regime influenced by matrix stiffness and demonstrating a finite maximum radius in experiments with Bacillus subtilis biofilms.

Contribution

The paper introduces a poroelastic model for biofilm growth under elastic confinement, highlighting a novel self-similar expansion regime and finite size limitation.

Findings

Identification of a new self-similar growth regime

Experimental validation with Bacillus subtilis biofilms

Finite maximum radius due to matrix stiffness

Abstract

Bacteria often form surface-bound communities, embedded in a self-produced extracellular matrix, called biofilms. Quantitative studies of their growth have typically focused on unconfined expansion above solid or semi-solid surfaces, leading to exponential radial growth. This geometry does not accurately reflect the natural or biomedical contexts in which biofilms grow in confined spaces. Here we consider one of the simplest confined geometries: a biofilm growing laterally in the space between a solid surface and an overlying elastic sheet. A poroelastic framework is utilised to derive the radial growth rate of the biofilm; it reveals an additional self-similar expansion regime, governed by the stiffness of the matrix, leading to a finite maximum radius, consistent with our experimental observations of growing $Bacillus~subtilis$ biofilms confined by PDMS.