Implication of molding hydrogel surfaces on bacterial surface sensing and bacterial adhesion

Bacterial adhesion onto a surface is a complicated process involving initial surface sensing and reversible surface adhesion, phenotypic adaptations, and irreversible adhesion to surfaces leading to biofilm formation. These biofilms, composed of microbial communities embedded in extracellular polymeric substances, provide bacteria with mechanical stability and protection against antibiotics. Therefore, to inhibit biofilm-associated infections, it is attractive to interfere with bacterial surface sensing and hinder the following bacterial adhesion. In this study, we investigated the effect of hydrogel surface molding on bacterial sensing and adhesion. Agarose gels were molded by different materials including glass, PDMS, and unmolded, and bacterial adhesion was assessed after a 1-hour incubation. Results showed a molding-dependent response with a higher bacterial adhesion on glass-molded gels than PDMS-molded or unmolded gels. Various mutants have been applied to understand how bacteria respond to different surfaces. The mutant deficient in a cell-surface-exposed protein PilY1, involved in mediating surface mechanosensing, exhibited equal adhesion across all gels, indicating its important role in surface sensing. Nanoindentation was performed to study changes in surface mechanical properties. Atomic force microscopy was also applied to characterize surface morphology. This work reveals how bacteria regulate their adhesion behavior in response to surface property changes.