Numerical model maps mechanics of complex biofilms

As microscopic colonies that thrive on solid surfaces when in contact with moisture, biofilms feature extracellular matrices that protect bacteria, help them resist antibiotics, and facilitate their spread. A menace in hospitals, food sector settings, and other scenarios, surface biofilm formation represents a major health threat and a significant concern for many industries.

Because biofilm mechanics play a key role in controlling biofilm formation, understanding their properties has been a longstanding priority. Along with experimental in vivo and in vitro approaches, numerical models have been developed to characterize biofilm viscoelasticity.

In the last two decades, phase-field and mesoscale modeling have enabled better understanding of biofilm structural and rheological properties. While such understanding can help maintain structural integrity and reduce human exposure to pathogens, the success of the modeling depends on multiple parameters to mimic extracellular matrix behaviors under stress.

Martín-Roca et al. use a novel mesoscale numerical tool to map rheological biofilm features within their mechano-structural landscapes, using Pseudomonas fluorescens – a common, gram-negative rod-shaped bacteria – as their subject.

“The viscoelasticity predicted by the numerical model was subject to experimental validation by measuring the ex situ responses of biofilms containing the same bacteria grown either under static conditions or via intense shear stimuli,” said author Chantal Valeriani.

The study’s dissipative particle dynamics simulation technique appears promising for forecasting rheological behaviors of extremely complex biofilms, as it allows for examination of nonlinear shear responses at variable strain amplitudes and frequencies.

“Our proposed method makes steps toward a more realistic forecasting of conservative and dissipative rheological features in complex biofilm structures,” said Valeriani. “This microscopic approach, which cannot be replicated experimentally, produces complementary information needed to understand biofilm mechanics.”

Source: “Rheology of Pseudomonas fluorescens biofilms: From experiments to DPD mesoscopic modelling,” by José Martín-Roca, Valentino Bianco, Francisco Alarcón, Ajay K. Monnappa, Paolo Natale, Francisco Monroy, Belen Orgaz, Ivan López-Montero, and Chantal Valeriani, Journal of Chemical Physics (2023). The article can be accessed at http://doi.org/10.1063/5.0131935 .