The TcaR-CtsR regulatory cascade governs multi-stress tolerance and biofilm formation in foodborne Staphylococcus aureus.

Staphylococcus aureus exhibits remarkable resilience to environmental stresses, largely governed by complex transcriptional regulatory networks. While CtsR is a well-established repressor of the heat shock response in Gram-positive bacteria, its role in S. aureus extends beyond proteotoxic stress management. In this study, using a foodborne S. aureus strain RMSA49, we demonstrated that CtsR is critical for biofilm formation, glycopeptide antibiotic susceptibility, and multi-stress tolerance to heat, desiccation, oxidative, and salt stresses. Genetic disruption of ctsR significantly impaired biofilm development and increased bacterial sensitivity to vancomycin and teicoplanin. Furthermore, we identified TcaR as a direct upstream regulator of ctsR, binding specifically to its promoter region, as confirmed by EMSA. This TcaR-CtsR regulatory cascade represents a novel layer of control in the stress adaptation mechanism of S. aureus. Our findings expand the functional scope of CtsR and provide new insights into the molecular basis of stress resilience and antibiotic susceptibility in this pathogen, highlighting potential targets for controlling S. aureus in both food safety and clinical contexts.