Differential growth of wrinkled biofilms

TL;DR

This paper presents a hybrid model combining biological and mechanical processes to study biofilm development, revealing how cellular differentiation and mechanical stresses lead to wrinkled structures on air-agar interfaces.

Contribution

It introduces a novel integrated model that links cellular behavior, gene regulation, and mechanical deformation to explain biofilm morphology and wrinkling phenomena.

Findings

Reproduces wrinkled biofilm structures observed experimentally.

Shows how stiffness gradients cause wrinkle branching.

Captures spatial distribution of differentiated cells in biofilms.

Abstract

Biofilms are antibiotic-resistant bacterial aggregates that grow on moist surfaces and can trigger hospital-acquired infections. They provide a classical example in biology where the dynamics of cellular communities may be observed and studied. Gene expression regulates cell division and differentiation, which affect the biofilm architecture. Mechanical and chemical processes shape the resulting structure. We gain insight into the interplay between cellular and mechanical processes during biofilm development on air-agar interfaces by means of a hybrid model. Cellular behavior is governed by stochastic rules informed by a cascade of concentration fields for nutrients, waste and autoinducers. Cellular differentiation and death alter the structure and the mechanical properties of the biofilm, which is deformed according to Foppl-Von Karman equations informed by cellular processes and the interaction with the substratum. Stiffness gradients due to growth and swelling produce wrinkle branching. We are able to reproduce wrinkled structures often formed by biofilms on air-agar interfaces, as well as spatial distributions of differentiated cells commonly observed with B. subtilis.