MD simulations provided a detailed, atomistic view of Lugdunin's mechanism of action, showing that multiple peptide molecules assemble cooperatively to form a nanotube that spans the entire thickness of the bacterial membrane (Figure B and C). This nanotube remains stable on the microsecond timescale and has a diameter comparable to gramicidin and compatible with the passage of ions . MD simulations further revealed that Lugdunin rapidly inserts into the membranes of S. aureus and B. subtilis [100], with a slightly higher partitioning affinity for the B. subtilis membrane, a trend confirmed by experimental findings . Interestingly, while Lugdunin's neutral and lipophilic nature facilitates its membrane insertion, it is repelled by the negatively charged phosphates and Kdo (3-Deoxy-D-manno-oct-2-ulosonic acid) residues found in the lipopolysaccharide (LPS) of the outer membrane of Gram-negative bacteria, such as E. coli (unpublished data). However, despite this repulsion, Lugdunin exhibited potent activity against E. coli with a compromised outer membrane . The latter finding poses hopes for its use as a broad-spectrum antibiotic in association with outer membrane-permeabilizing agents, an approach that is gaining attraction to re-purpose Gram-positive active molecules against the emergence of drugresistant Gram-negative strains .