title: Structure and biological roles of Sinorhizobium fredii HH103 exopolysaccharide.
abstract: Here we report that the structure of the Sinorhizobium fredii HH103 exopolysaccharide (EPS) is composed of glucose, galactose, glucuronic acid, pyruvic acid, in the ratios 5∶2∶2∶1 and is partially acetylated. A S. fredii HH103 exoA mutant (SVQ530), unable to produce EPS, not only forms nitrogen fixing nodules with soybean but also shows increased competitive capacity for nodule occupancy. Mutant SVQ530 is, however, less competitive to nodulate Vigna unguiculata. Biofilm formation was reduced in mutant SVQ530 but increased in an EPS overproducing mutant. Mutant SVQ530 was impaired in surface motility and showed higher osmosensitivity compared to its wild type strain in media containing 50 mM NaCl or 5% (w/v) sucrose. Neither S. fredii HH103 nor 41 other S. fredii strains were recognized by soybean lectin (SBL). S. fredii HH103 mutants affected in exopolysaccharides (EPS), lipopolysaccharides (LPS), cyclic glucans (CG) or capsular polysaccharides (KPS) were not significantly impaired in their soybean-root attachment capacity, suggesting that these surface polysaccharides might not be relevant in early attachment to soybean roots. These results also indicate that the molecular mechanisms involved in S. fredii attachment to soybean roots might be different to those operating in Bradyrhizobium japonicum.
authors.affiliation: IFAPA, Centro las Torres-Tomejil, Apartado Oficial 41200, Alcalá del Río, (Sevilla), Spain.
authors.forename: Dulce N
authors.initials: DN
authors.lastname: Rodríguez-Navarro
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Rodríguez-Carvajal
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Sebastián
authors.initials: S
authors.lastname: Acosta-Jurado
authors.affiliation: Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Granada, Spain.
authors.forename: María J
authors.initials: MJ
authors.lastname: Soto
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Margaret
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Crespo-Rivas
authors.affiliation: Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Granada, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Sanjuan
authors.affiliation: IFAPA, Centro las Torres-Tomejil, Apartado Oficial 41200, Alcalá del Río, (Sevilla), Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Temprano
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gil-Serrano
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: José E
authors.initials: JE
authors.lastname: Ruiz-Sainz
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Vinardell
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002240:Carbohydrate Sequence; D007887:Fabaceae / Q000382:microbiology; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation; D009997:Osmotic Pressure; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000378:metabolism; D042181:Sinorhizobium fredii / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; D016695:Glycosyltransferases