Staphylococcus epidermidis DnaK chaperone protein inhibits Staphylococcus aureus CIP 107093 biofilm formation and induces an accumulation of the exfoliative toxin A

Staphylococcus aureus and Staphylococcus epidermidis are Gram-positive bacteria commonly found in human skin microbiota, and produce biofilms that are associated with skin dysbiosis, as in acne or in atopic dermatitis. The Calcitonin Gene Related Peptide (CGRP) is a human peptide involved in skin inflammation. We previously showed that CGRP activates virulence of S. epidermidis MFP04, and that the DnaK chaperone protein is overexpressed in the secretome of the virulent, CGRP-activated S. epidermidis. In this study, we explored a potential new role of S. epidermidis DnaK in biofilm formation, in both S. aureus and S. epidermidis. We showed that recombinant S. epidermidis DnaK differently affects biofilm formation, whether in two skin commensal staphylococcal strains (S. aureus MFP03 and S. epidermidis MFP04), or in a clinical S. aureus strain (CIP 107093). In S. aureus CIP 107093, biofilm formation was most significantly inhibited. This inhibition involves both the Substrate-Binding Domain and the Nucleotide-Binding Domain of DnaK, and is associated with an accumulation of the exfoliative toxin A (ETA). These results indicate that S. epidermidis DnaK may contribute to the regulation of S. aureus biofilm formation, suggesting a cross-species regulatory role of DnaK within the skin microbiota.