The Exo-Polysaccharide Component of Extracellular Matrix is Essential for the Viscoelastic Properties of Bacillus subtilis Biofilms

Abstract

Bacteria are known to form biofilms on various surfaces. Biofilms are multicellular aggregates, held together by an extracellular matrix, which is composed of biological polymers. Three principal components of the biofilm matrix are exopolysaccharides (EPS), proteins, and nucleic acids. The biofilm matrix is essential for biofilms to remain organized under mechanical stress. Thanks to their polymeric nature, biofilms exhibit both elastic and viscous mechanical characteristics; therefore, an accurate mechanical description needs to take into account their viscoelastic nature. Their viscoelastic properties, including during their growth dynamics, are crucial for biofilm survival in many environments, particularly during infection processes. How changes in the composition of the biofilm matrix affect viscoelasticity has not been thoroughly investigated. In this study, we used interfacial rheology to study the contribution of the EPS component of the matrix to viscoelasticity of Bacillus subtilis biofilms. Two strategies were used to specifically deplete the EPS component of the biofilm matrix, namely (i) treatment with sub-lethal doses of vitamin C and (ii) seamless inactivation of the eps operon responsible for biosynthesis of the EPS. In both cases, the obtained results suggest that the EPS component of the matrix is essential for maintaining the viscoelastic properties of bacterial biofilms during their growth. If the EPS component of the matrix is depleted, the mechanical stability of biofilms is compromised and the biofilms become more susceptible to eradication by mechanical stress.

Systems view of Bacillus subtilis pellicle development

“…There are only a few direct studies of the temporal dynamics and mechanical stability in growing bacterial pellicles 40 – 42 . In most studies, the mechanical properties and morphology of the B. subtilis pellicles were monitored indirectly, ex situ , focusing only on the water–air interface without taking into account the events in the bulk of the liquid 13 , 32 , 43 , 44 .…”

“…Viscoelasticity of the biofilm is determined by bacterial cells density, the extracellular matrix 28 , 47 , cell chain entanglement, and crosslinking 48 . The study of the rheological properties of the interfacial pellicles has greatly improved our understanding of pellicle structures 41 , 42 . With interfacial rheology, Rühs et al monitored the mechanics of the newly formed pellicle of B. subtilis and a mutant strain that did not produce surfactin in the LB medium.…”

Chickpea-Derived Prebiotic Substances Trigger Biofilm Formation by Bacillus subtilis

“…In this study, the CPF supplementation triggered biofilm formation likely via increasing the available micro-and macronutrients, although it is also possible that the CPF may have created a favorable osmotic pressure that signals bacterial cells to opt the biofilm formation pathway [24,25]. In addition, induction in biofilm formation resulted in significant upregulation of tapA operon was exclusively related to the CPF.…”

Graphene-Based Sensor for Detection of Bacterial Pathogens

“…Biofilms are dynamic multicellular 3D structures developed by microorganisms [36,37]. The aggregation or adhesion of microbial cells on a biotic/abiotic surface is a key primary stage for such biofilm formation [38].…”