Illuminating Bacterial Defenses: Differential Proteomic Responses of Staphylococcus aureus to Sublethal aPDI with Rose Bengal and New Methylene Blue

This study elucidates the sublethal effects of antimicrobial photodynamic inactivation (aPDI) on Staphylococcus aureus proteomes, uncovering adaptive stress responses. These findings enhance our understanding of bacterial resistance mechanisms and support the development of innovative non-antibiotic therapies. S. aureus strains were subjected to sublethal aPDI using Rose Bengal (RB) or New Methylene Blue (NMB) with custom LED illumination. Protein lysates were prepared using FASP and STAGE-tip desalting, then analysed by SWATH-MS at 0, 1, and 2 hours post-treatment. Data were processed and annotated. Photodynamic treatment with RB and NMB modulated protein expression in three S. aureus strains. RB affected 99 proteins (28 common across strains), while NMB altered 57 (4 common). Thirty-four proteins were shared overall, with most changes involving ribosomal, translational, and biosynthetic functions. The results reveal photosensitizer-specific responses. RB induced a more consistent proteomic profile compared to NMB, providing insights for optimizing photodynamic inactivation strategies.