Antibacterial mechanism of geraniol against Staphylococcus aureus by targeting the cell membrane

Geraniol exhibits strong antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) in both in vitro and in vivo; yet its underlying mechanism remains incompletely understood. Our study system-atically characterized the antibacterial mode of action of geraniol using flow cytometry, fluorescence spectroscopy, electron microscopy, and molecular dynamics simulations. The results showed that geraniol readily partitions into the lipid bilayer and disrupts membrane integrity, with 81.95% of cells exhibiting membrane damage at 1.380 mg/mL. Consistently, geraniol treatment increased membrane fluidity, as indicated by a reduction in fluorescence polarization from 0.410 to 0.380, and was associated with conformational alterations in membrane proteins. These membrane perturbations were accompanied by extensive downstream damage, including leakage of intracellular components, with extracellular levels increasing by 9.61-fold for DNA, 11.82-fold for RNA, and 15.92-fold for proteins. Additionally, ultrastructural analyses revealed cell wall thinning from 0.037 μm to 0.026 μm and marked DNA condensation. Collectively, these findings indicate that the MRSA cell membrane represents a primary target of geraniol, with subsequent structural damage likely resulting from severe membrane dysfunction and disruption of cellular homeostasis. This study provides mechanistic insights supporting the potential development of geraniol as a membrane-targeting antibacterial agent.