title: Detailed structural analysis of the peptidoglycan of the human pathogen Neisseria meningitidis.
abstract: We used reverse-phase high pressure liquid chromatography (HPLC), matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and post source decay analysis (MALDI-PSD) to determine the muropeptide composition of the human pathogen Neisseria meningitidis. Structural assignment was determined for 28 muropeptide species isolated after HPLC separation and purification. Fourteen of these muropeptides were O-acetylated to different degrees. We identified the entire O-acetylation spectrum of dimers and trimers both in muropeptides and 1,6-anhydromuropeptides. On average, one of three disaccharides was O-acetylated. Furthermore, the degree of cross-linking of the N. meningitidis peptidoglycan was around 39% in all the strains analyzed. MALDI-PSD analysis of several muropeptide species indicated that meningococci only synthesize D-alanyl-meso-diaminopimelate cross-bridges. No muropeptides representative of covalent linkages of lipoproteins to the peptidoglycan could be identified, unlike in Escherichia coli. Finally, comparison of the muropeptide composition of penicillin-susceptible and penicillin-intermediate clinical strains of meningococci showed a positive correlation between the minimum inhibitory concentration (MIC) of penicillin G and the amount of muropeptides carrying an intact pentapeptide chain in the peptidoglycan. This suggests that reduced susceptibility to penicillin G in N. meningitidis is associated with a decrease in d,d-carboxypeptidase activity and/or D,D-transpeptidase activity.
authors.affiliation: Unité des Neisseria and Centre National de Référence des Méningocoques, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris Cedex 15, France.
authors.forename: Aude
authors.initials: A
authors.lastname: Antignac
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Rousselle
authors.forename: Abdelkader
authors.initials: A
authors.lastname: Namane
authors.forename: Agnès
authors.initials: A
authors.lastname: Labigne
authors.forename: Muhamed-Kheir
authors.initials: MK
authors.lastname: Taha
authors.forename: Ivo G
authors.initials: IG
authors.lastname: Boneca
mesh_terms: D002236:Carbohydrate Conformation; D002851:Chromatography, High Pressure Liquid; D008826:Microbial Sensitivity Tests; D009345:Neisseria meningitidis / Q000737:chemistry* / Q000187:drug effects; D010400:Penicillin G / Q000494:pharmacology; D010457:Peptidoglycan / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D010457:Peptidoglycan; D010400:Penicillin G