title: Structure of the O-antigen of the main lipopolysaccharide isolated from Sinorhizobium fredii SMH12.
abstract: The lipopolysaccharide of Sinorhizobium fredii SMH12, a wide-range host bacterium isolated from nodulated soybean plants growing in Vietnam, has been studied. Isolation of lipopolysaccharide by the phenol-water method leads to a mixture of two polysaccharides; polyacrylamide gel electrophoresis indicates that both are possibly lipopolysaccharides. The structures of the O-antigen of the main lipopolysaccharide and its deacetylated form are determined by sugar and methylation analysis, partial hydrolysis, lithium degradation, ESI-MS/MS, and NMR studies. Here we show that the fast-growing S. fredii SMH12 produces a lipopolysaccharide whose O-antigen has a repeating unit consisting of the trisaccharide -->4)-alpha-D-Gal pA-(1-->3)-2-O-Ac-alpha-L-Rha p-(1-->3)-2-O-Ac-alpha-D-Man p-(1-->. The position O-6 of the mannose residue in the repeating unit is unsubstituted, acetylated, or methylated in an approximate ratio 1:1:2. The tandem mass spectrometry studies rule out both an alternating and a random distribution of methyl groups and suggest the existence of zones in the polysaccharide rich in methyl groups interspersed with zones without methyl groups.
authors.affiliation: Department of Organic Chemistry, Faculty of Chemistry, University of Seville, 41071 Sevilla, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Fernández de Córdoba
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Rodríguez-Carvajal
authors.forename: Pilar
authors.initials: P
authors.lastname: Tejero-Mateo
authors.forename: Javier
authors.initials: J
authors.lastname: Corzo
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Gil-Serrano
mesh_terms: D008070:Lipopolysaccharides / Q000737:chemistry / Q000302:isolation & purification; D015394:Molecular Structure; D019081:O Antigens / Q000737:chemistry* / Q000302:isolation & purification*; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D042181:Sinorhizobium fredii
chemical_list: D008070:Lipopolysaccharides; D019081:O Antigens; D011135:Polysaccharides, Bacterial