Mechanical Properties of Bacterial Biofilms

Bacterial biofilms are structured communities of cells encased within a self-produced extracellular polymeric substance (EPS) matrix. Mechanically, biofilms exhibit viscoelastic behaviour, combining fluid-like and solid-like characteristics that enable them to resist shear forces, adapt to dynamic environments and withstand mechanical perturbations. The EPS matrix, composed of polysaccharides, proteins and nucleic acids, cross-links cells into a network whose stiffness and yield stress depend on polymer composition, cell density and environmental conditions. Mechanical properties are commonly assessed via rheometry, atomic force microscopy and indentation techniques, providing metrics such as elastic modulus, viscosity and yield strength. Such measurements reveal how biofilm architecture evolves through structural transitions—ranging from weak gels to colloidal glasses—and how mechanical toughness contributes to persistence on surfaces, in clinical infections and industrial systems. Understanding these properties is critical for controlling biofilms in medical, industrial and environmental contexts, informing strategies from anti-fouling coatings to targeted enzymatic dispersal. Integration of theoretical models from colloid and polymer physics with experimental mechanics offers insight into global biofilm resilience and points towards novel approaches for biofilm management.

Research from Nature Portfolio

Non-destructive imaging via optical coherence tomography has been refined to quantify biofilm density by eliminating auto-scaling artefacts and correlating re-scaled signal intensities with volumetric bacterial counts. This approach enables direct comparison of structural density across diverse mono- and multi-species biofilms, enhancing the precision of mechanical interpretation without staining or disruption. Mechanical indentation and shear rheometry of Pseudomonas aeruginosa variants isolated from chronic lung infections demonstrate that mucoid and rugose small-colony variants progressively stiffen and exhibit more elastic-solid behaviour over time. These changes predict reduced clearance by mucociliary or cough mechanisms, highlighting viscoelasticity as a virulence trait. Artificially assembled staphylococcal biofilms created through colloidal self-assembly of cells and polysaccharides reproduce natural viscoelastic properties. pH-induced phase instability triggers matrix solubilisation and biofilm disassembly, suggesting that exploitation of colloidal interactions can inform strategies for controlled biofilm removal.

Mechanical Properties of Bacterial Biofilms publication trend

The graph below shows the total number of articles in mechanical properties of bacterial biofilms across all publications each year (not limited to Nature Index journals).

Technical terms

Biofilm: A surface-attached community of microbial cells encased in a self-produced polymeric matrix.

Extracellular polymeric substance (EPS): The mixture of polysaccharides, proteins, nucleic acids and lipids that forms the biofilm matrix.

Viscoelasticity: A material property exhibiting both viscous flow and elastic deformation under stress.

Rheology: The study of flow and deformation characteristics of materials under applied forces.

Elastic modulus: A measure of material stiffness defined as the ratio of stress to reversible strain.

Yield stress: The threshold stress above which a material begins to flow irreversibly.

Colloidal gel: A networked structure of particles dispersed in a polymer matrix that exhibits solid-like behaviour at low stresses.

References

1. Microstructural and Rheological Transitions in Bacterial Biofilms. Advanced Science (2023).
2. EPS—Then and Now. Microorganisms (2016).
3. Towards standardized mechanical characterization of microbial biofilms: analysis and critical review. npj Biofilms and Microbiomes (2018).
4. Biofilm mechanics: Implications in infection and survival. Biofilm (2019).
5. Bacterial Density and Biofilm Structure Determined by Optical Coherence Tomography. Scientific Reports (2019).
6. Viscoelastic properties of Pseudomonas aeruginosa variant biofilms. Scientific Reports (2018).
7. Artificial biofilms establish the role of matrix interactions in staphylococcal biofilm assembly and disassembly. Scientific Reports (2015).
8. Nonlinear rheological characteristics of single species bacterial biofilms. npj Biofilms and Microbiomes (2020).