title: New insights into the mode of action of the lantibiotic salivaricin B.
abstract: Salivaricin B is a 25 amino acid polycyclic peptide belonging to the type AII lantibiotics and first shown to be produced by Streptococcus salivarius. In this study we describe the bactericidal mode of action of salivaricin B against susceptible Gram-positive bacteria. The killing action of salivaricin B required micro-molar concentrations of lantibiotic whereas the prototype lantibiotic nisin A was shown to be potent at nano-molar levels. Unlike nisin A, salivaricin B did not induce pore formation or dissipate the membrane potential in susceptible cells. This was established by measuring the fluorescence of the tryptophan residue at position 17 when salivaricin B interacted with bacterial membrane vesicles. The absence of a fluorescence blue shift indicates a failure of salivaricin B to penetrate the membranes. On the other hand, salivaricin B interfered with cell wall biosynthesis, as shown by the accumulation of the final soluble cell wall precursor UDP-MurNAc-pentapeptide which is the backbone of the bacterial peptidoglycan. Transmission electron microscopy of salivaricin B-treated cells showed a reduction in cell wall thickness together with signs of aberrant septum formation in the absence of visible changes to cytoplasmic membrane integrity.
authors.affiliation: Division of Microbiology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala lumpur, Malaysia.
authors.forename: Abdelahhad
authors.initials: A
authors.lastname: Barbour
authors.affiliation: Department of Microbiology and Immunology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
authors.forename: John
authors.initials: J
authors.lastname: Tagg
authors.affiliation: Department of Chemistry, Faculty of Science, Sultan Qaboos University, P.O. Box 36, Postal Code 123, Muscat, Sultanate of Oman.
authors.forename: Osama K
authors.initials: OK
authors.lastname: Abou-Zied
authors.affiliation: Division of Microbiology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala lumpur, Malaysia.
authors.forename: Koshy
authors.initials: K
authors.lastname: Philip
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000494:pharmacology; D001430:Bacteriocins / Q000737:chemistry / Q000494:pharmacology*; D002473:Cell Wall / Q000187:drug effects / Q000648:ultrastructure; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000648:ultrastructure; D008826:Microbial Sensitivity Tests; D016982:Micrococcus luteus / Q000187:drug effects / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D013297:Streptococcus pyogenes / Q000187:drug effects / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001430:Bacteriocins; C082674:salivaricin A