title: Ramoplanin at bactericidal concentrations induces bacterial membrane depolarization in Staphylococcus aureus.
abstract: Ramoplanin is an actinomycetes-derived antibiotic with broad-spectrum activity against Gram-positive bacteria that has been evaluated in clinical trials for the treatment of gastrointestinal vancomycin-resistant enterococci (VRE) and Clostridium difficile infections. Recent studies have proposed that ramoplanin binds to bacterial membranes as a C2 symmetrical dimer that can sequester Lipid II, which causes inhibition of cell wall peptidoglycan biosynthesis and cell death. In this study, ramoplanin was shown to bind to anionic and zwitterionic membrane mimetics with a higher affinity for anionic membranes and to induce membrane depolarization of methicillin-susceptible Staphylococcus aureus (MSSA) ATCC 25923 at concentrations at or above the minimal bactericidal concentration (MBC). The ultrastructural effects of ramoplanin on S. aureus were also examined by transmission electron microscopy (TEM), and this showed dramatic changes to bacterial cell morphology. The correlation observed between membrane depolarization and bacterial cell viability suggests that this mechanism may contribute to the bactericidal activity of ramoplanin.
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Mu
authors.initials: M
authors.lastname: Cheng
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Johnny X
authors.initials: JX
authors.lastname: Huang
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Soumya
authors.initials: S
authors.lastname: Ramu
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Butler
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia m.cooper@uq.edu.au.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Cooper
mesh_terms: D000838:Anions / Q000737:chemistry; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology*; D002470:Cell Survival; D002473:Cell Wall / Q000378:metabolism / Q000502:physiology; D047630:Depsipeptides / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009561:Nisin / Q000494:pharmacology; D011485:Protein Binding; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects*; D017334:Teicoplanin / Q000494:pharmacology; D014640:Vancomycin / Q000494:pharmacology
chemical_list: D000838:Anions; D000900:Anti-Bacterial Agents; D047630:Depsipeptides; C041438:ramoplanin; D009561:Nisin; D017334:Teicoplanin; D014640:Vancomycin