Collagen-mediated biofilm formation and fibrillar organization in Staphylococcus epidermidis

The symbiotic skin bacterium Staphylococcus epidermidis moisturizes human skin, contributes to protection against external pathogens, and supports innate immune stimulation. However, the interaction between collagen, a major skin protein, and S. epidermidis remains insufficiently explored. In this study, biofilm development was investigated using scanning electron microscopy with ionic liquid pretreatment, confocal laser scanning microscopy, biofilm quantification assays, and growth curve analysis. In the presence of collagen, cells adhered to the substrate, secreted microvesicles, formed web-like intercellular fibrillar connections, and became embedded in an extracellular polymeric substance-like matrix. Confocal microscopy and quantitative analyses showed that collagen supplementation significantly increased biofilm thickness and biomass over time, with biomass approximately 1.6-fold higher at 36 h, while growth curves indicated minimal effects on bacterial proliferation. As biofilms matured, surface cells exhibited organized alignment, and thread-like fibrils connected cells in less dense regions. These findings suggest that collagen promotes distinct biofilm architectures and influences the structural development of biofilms.