Lugdunin: Ionophore mechanism of action. Lugdunin is a cyclic peptide, isolated from a strain of nasal Staphylococcus lugdunensis . Its unique structure (depicted in Figure ) alternates D-and L-amino acids and features a thiazolidine ring, a key component for Lugdunin's activity . This unusual configuration plays a pivotal role in how Lugdunin interacts with bacterial membranes. The peptide molecules form membrane pores, stabilized by hydrogen bonds between the amide nitrogen and oxygen atoms, creating an intermolecular -sheet-like structure inside the membrane [100](Figure ).