The Physics of Biofilms -- An Introduction

TL;DR

This paper reviews the physical principles underlying biofilm formation, structure, and dynamics, highlighting mechanisms like cell motility and adhesion, and discusses experimental and theoretical approaches to understanding their complex behavior.

Contribution

It provides a comprehensive overview of the physical processes in biofilm development, integrating experimental and theoretical insights into their hierarchical and heterogeneous nature.

Findings

Biofilms behave as viscoelastic fluids with complex dynamics.

Cell motility and adhesion are key to biofilm initiation and stability.

Progress in measuring biofilm physical properties is advancing understanding.

Abstract

Biofilms are complex, self-organized consortia of microorganisms that produce a functional, protective matrix of biomolecules. Physically, the structure of a biofilm can be described as an entangled polymer network which grows and changes under the effect of gradients of nutrients, cell differentiation, quorum sensing, bacterial motion, and interaction with the environment. Its development is complex, and constantly adapting to environmental stimuli. Here, we review the fundamental physical processes the govern the inception, growth and development of a biofilm. Two important mechanisms guide the initial phase in a biofilm life cycle: (\emph{i}) the cell motility near or at a solid interface, and (\emph{ii}) the cellular adhesion. Both processes are crucial for initiating the colony and for ensuring its stability. A mature biofilm behaves as a viscoelastic fluid with a complex, history-dependent dynamics. We discuss progress and challenges in the determination of its physical properties. Experimental and theoretical methods are now available that aim at integrating the biofilm's hierarchy of interactions, and the heterogeneity of composition and spatial structures. We also discuss important directions in which future work should be directed.