title: Capsular glucan and intracellular glycogen of Mycobacterium tuberculosis: biosynthesis and impact on the persistence in mice.
abstract: Mycobacterium tuberculosis and other pathogenic mycobacterial species produce large amounts of a glycogen-like alpha-glucan that represents the major polysaccharide of their outermost capsular layer. To determine the role of the surface-exposed glucan in the physiology and virulence of these bacteria, orthologues of the glg genes involved in the biosynthesis of glycogen in Escherichia coli were identified in M. tuberculosis H37Rv and inactivated by allelic replacement. Biochemical analyses of the mutants and complemented strains indicated that the synthesis of glucan and glycogen involves the alpha-1,4-glucosyltransferases Rv3032 and GlgA (Rv1212c), the ADP-glucose pyrophosphorylase GlgC (Rv1213) and the branching enzyme GlgB (Rv1326c). Disruption of glgC reduced by half the glucan and glycogen contents of M. tuberculosis, whereas the inactivation of glgA and Rv3032 affected the production of capsular glucan and glycogen, respectively. Attempts to disrupt Rv3032 in the glgA mutant were unsuccessful, suggesting that a functional copy of at least one of the two alpha-1,4-glucosyltransferases is required for growth. Importantly, the glgA mutant was impaired in its ability to persist in mice, suggesting a role for the capsular glucan in the persistence phase of infection. Unexpectedly, GlgB was found to be an essential enzyme.
authors.affiliation: Université Paul Sabatier (Toulouse III) 118, route de Narbonne, 31062-Toulouse cedex 04, France.
authors.forename: Tounkang
authors.initials: T
authors.lastname: Sambou
authors.forename: Premkumar
authors.initials: P
authors.lastname: Dinadayala
authors.forename: Gustavo
authors.initials: G
authors.lastname: Stadthagen
authors.forename: Nathalie
authors.initials: N
authors.lastname: Barilone
authors.forename: Yann
authors.initials: Y
authors.lastname: Bordat
authors.forename: Patricia
authors.initials: P
authors.lastname: Constant
authors.forename: Florence
authors.initials: F
authors.lastname: Levillain
authors.forename: Olivier
authors.initials: O
authors.lastname: Neyrolles
authors.forename: Brigitte
authors.initials: B
authors.lastname: Gicquel
authors.forename: Anne
authors.initials: A
authors.lastname: Lemassu
authors.forename: Mamadou
authors.initials: M
authors.lastname: Daffé
authors.forename: Mary
authors.initials: M
authors.lastname: Jackson
mesh_terms: D015061:1,4-alpha-Glucan Branching Enzyme / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004269:DNA, Bacterial / Q000235:genetics; D005260:Female; D055786:Gene Knockout Techniques; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005936:Glucans / Q000096:biosynthesis*; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000235:genetics / Q000378:metabolism; D006003:Glycogen / Q000096:biosynthesis*; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D014376:Tuberculosis / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005936:Glucans; D006003:Glycogen; D015061:1,4-alpha-Glucan Branching Enzyme; D051599:Glucose-1-Phosphate Adenylyltransferase