Olikomycin A Disrupts Gram‐Positive Bacterial Membranes Through Calcium‐Dependent Binding to Phosphatidylglycerol

ABSTRACT

Calcium‐dependent antibiotics (CDAs) represent an important class of antimicrobial agents active against Gram‐positive pathogens. Olikomycin A, produced by Streptomyces ghanaensis Δ wblA , displays potent activity against multidrug‐resistant bacteria; however, its molecular mode of action remained unclear. In this study, we investigated the interaction of olikomycin A with bacterial membrane lipids. Phospholipid antagonization assays demonstrated a calcium‐dependent interaction with phosphatidylglycerol (PG), a major anionic phospholipid of Gram‐positive membranes. Cryo‐electron microscopy and fluorescence microscopy using model membranes revealed rapid membrane disruption induced by olikomycin A, resulting in vesicle deformation and fragmentation. Compared with the clinically used lipopeptide daptomycin, olikomycin A caused markedly faster and more extensive membrane damage. Furthermore, treatment of Staphylococcus aureus with olikomycin A in the presence of calcium resulted in rapid cellular aggregation consistent with severe membrane perturbation. These findings indicate that olikomycin A targets bacterial membranes via calcium‐dependent binding to PG and disrupts membrane integrity through a mechanism distinct from daptomycin.