Integrated Phenotypic and Transcriptomic Analyses Unveil the Antibacterial Mechanism of Punicalagin Against Methicillin-Resistant Staphylococcus aureus (MRSA)

The growing emergence of multidrug-resistant bacterial pathogens drives the need for new antibacterial agents. Punicalagin exhibits efficacy against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA), but its specific antibacterial mechanisms remain unclear. This study unveiled the specific antibacterial mechanism of punicalagin against MRSA via phenotypic and transcriptomic analyses. Punicalagin was found to induce severe cell wall damage and membrane disruption. Competitive binding assays identified lipoteichoic acid (LTA) as a potential target, and transcriptomic analysis further revealed that punicalagin downregulated key genes involved in cell wall synthesis (<i>mur</i>A, <i>mur</i>E) and LTA biosynthesis (<i>dlt</i>A-D), consistent with the disruption of the cell wall. Additionally, punicalagin disrupted membrane homeostasis by inhibiting fatty acid synthesis (<i>fab</i>D, <i>fab</i>Z) and amino acid metabolism (<i>dap</i>A, <i>dap</i>B), leading to increased membrane permeability, which aligned with the phenotypic manifestations of membrane damage. Collectively, this work links phenotypic changes to specific gene expression patterns, unveiling that punicalagin inactivates MRSA via the multi-pathway regulation of the cell wall (LTA) and membrane function-providing insights for combating antibiotic-resistant pathogens in food safety and clinical settings.