title: Structure of the cell envelope of corynebacteria: importance of the non-covalently bound lipids in the formation of the cell wall permeability barrier and fracture plane.
abstract: With the recent success of the heterologous expression of mycobacterial antigens in corynebacteria, in addition to the importance of these bacteria in biotechnology and medicine, a better understanding of the structure of their cell envelopes was needed. A combination of molecular compositional analysis, ultrastructural appearance and freeze-etch electron microscopy study was used to arrive at a chemical model, unique to corynebacteria but consistent with their phylogenetic relatedness to mycobacteria and other members of the distinctive suprageneric actinomycete taxon. Transmission electron microscopy and chemical analyses showed that the cell envelopes of the representative strains of corynebacteria examined consisted of (i) an outer layer composed of polysaccharides (primarily a high-molecular-mass glucan and arabinomannans), proteins, which include the mycoloyltransferase PS1, and lipids; (ii) a cell wall glycan core of peptidoglycan-arabinogalactan which may contain other sugar residues and was usually esterified by corynomycolic acids; and (iii) a typical plasma membrane bilayer. Freeze-etch electron microscopy showed that most corynomycolate-containing strains exhibited a main fracture plane in their cell wall and contained low-molecular-mass porins, while the fracture occurred within the plasma membrane of strains devoid of both corynomycolate and pore-forming proteins. Importantly, in most strains, the amount of cell wall-linked corynomycolates was not sufficient to cover the bacterial surface; interestingly, the occurrence of a cell wall fracture plane correlated with the amount of non-covalently bound lipids of the strains. Furthermore, these lipids were shown to spontaneously form liposomes, indicating that they may participate in a bilayer structure. Altogether, the data suggested that the cell wall permeability barrier in corynebacteria involved both covalently linked corynomycolates and non-covalently bound lipids of their cell envelopes.
authors.affiliation: Institut de Pharmacologie et Biologie Structurale, Centre National de la Recherche Scientifique/Université Paul Sabatier (UMR 5089), 205 route de Narbonne, 31077, Toulouse Cedex 04, France1.
authors.forename: Virginie
authors.initials: V
authors.lastname: Puech
authors.affiliation: Centre de Génétique Moléculaire, CNRS, 91190 Gif-sur-Yvette, France5.|Laboratoire des Biomembranes, UMR 8619 CNRS-Université Paris-Sud, 91405 Orsay Cedex, France2.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Chami
authors.affiliation: Institut de Pharmacologie et Biologie Structurale, Centre National de la Recherche Scientifique/Université Paul Sabatier (UMR 5089), 205 route de Narbonne, 31077, Toulouse Cedex 04, France1.
authors.forename: Anne
authors.initials: A
authors.lastname: Lemassu
authors.affiliation: Institut de Pharmacologie et Biologie Structurale, Centre National de la Recherche Scientifique/Université Paul Sabatier (UMR 5089), 205 route de Narbonne, 31077, Toulouse Cedex 04, France1.
authors.forename: Marie-Antoinette
authors.initials: MA
authors.lastname: Lanéelle
authors.affiliation: Lehrstuhl für Biotechnologie, Biozentrum der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany3.
authors.forename: Bettina
authors.initials: B
authors.lastname: Schiffler
authors.affiliation: Institut Pasteur, Service de Microscopie électronique, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France4.
authors.forename: Pierre
authors.initials: P
authors.lastname: Gounon
authors.affiliation: Laboratoire des Biomembranes, UMR 8619 CNRS-Université Paris-Sud, 91405 Orsay Cedex, France2.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bayan
authors.affiliation: Lehrstuhl für Biotechnologie, Biozentrum der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany3.
authors.forename: Roland
authors.initials: R
authors.lastname: Benz
authors.affiliation: Institut de Pharmacologie et Biologie Structurale, Centre National de la Recherche Scientifique/Université Paul Sabatier (UMR 5089), 205 route de Narbonne, 31077, Toulouse Cedex 04, France1.
authors.forename: Mamadou
authors.initials: M
authors.lastname: Daffé
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis; D015153:Blotting, Western; D002462:Cell Membrane / Q000648:ultrastructure; D002463:Cell Membrane Permeability; D002473:Cell Wall / Q000737:chemistry / Q000648:ultrastructure; D003352:Corynebacterium / Q000737:chemistry / Q000648:ultrastructure*; D020285:Cryoelectron Microscopy; D004591:Electrophoresis, Polyacrylamide Gel; D005685:Galactans / Q000032:analysis; D008081:Liposomes / Q000032:analysis; D008351:Mannans / Q000032:analysis; D008562:Membrane Glycoproteins; D008563:Membrane Lipids / Q000032:analysis; D008854:Microscopy, Electron; D009161:Mycobacterium / Q000737:chemistry / Q000648:ultrastructure; D011135:Polysaccharides, Bacterial / Q000032:analysis / Q000737:chemistry / Q000648:ultrastructure*; D018272:Porins / Q000032:analysis
chemical_list: D001426:Bacterial Proteins; D005685:Galactans; D008081:Liposomes; D008351:Mannans; D008562:Membrane Glycoproteins; D008563:Membrane Lipids; D011135:Polysaccharides, Bacterial; D018272:Porins; C055764:S-layer proteins; C077000:PS1 protein, Corynebacterium glutamicum; C012189:arabinomannan; C005653:arabinogalactan