title: Structure and biosynthesis of two exopolysaccharides produced by Lactobacillus johnsonii FI9785.
abstract: Exopolysaccharides were isolated and purified from Lactobacillus johnsonii FI9785, which has previously been shown to act as a competitive exclusion agent to control Clostridium perfringens in poultry. Structural analysis by NMR spectroscopy revealed that L. johnsonii FI9785 can produce two types of exopolysaccharide: EPS-1 is a branched dextran with the unusual feature that every backbone residue is substituted with a 2-linked glucose unit, and EPS-2 was shown to have a repeating unit with the following structure: -6)-α-Glcp-(1-3)-β-Glcp-(1-5)-β-Galf-(1-6)-α-Glcp-(1-4)-β-Galp-(1-4)-β-Glcp-(1-. Sites on both polysaccharides were partially occupied by substituent groups: 1-phosphoglycerol and O-acetyl groups in EPS-1 and a single O-acetyl group in EPS-2. Analysis of a deletion mutant (ΔepsE) lacking the putative priming glycosyltransferase gene located within a predicted eps gene cluster revealed that the mutant could produce EPS-1 but not EPS-2, indicating that epsE is essential for the biosynthesis of EPS-2. Atomic force microscopy confirmed the localization of galactose residues on the exterior of wild type cells and their absence in the ΔepsE mutant. EPS2 was found to adopt a random coil structural conformation. Deletion of the entire 14-kb eps cluster resulted in an acapsular mutant phenotype that was not able to produce either EPS-2 or EPS-1. Alterations in the cell surface properties of the EPS-specific mutants were demonstrated by differences in binding of an anti-wild type L. johnsonii antibody. These findings provide insights into the biosynthesis and structures of novel exopolysaccharides produced by L. johnsonii FI9785, which are likely to play an important role in biofilm formation, protection against harsh environment of the gut, and colonization of the host.
authors.affiliation: From the Gut Health and Food Safety Programme, Institute of Food Research, Colney, Norwich NR4 7UA, United Kingdom.
authors.forename: Enes
authors.initials: E
authors.lastname: Dertli
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Colquhoun
authors.forename: A Patrick
authors.initials: AP
authors.lastname: Gunning
authors.forename: Roy J
authors.initials: RJ
authors.lastname: Bongaerts
authors.forename: Gwénaëlle
authors.initials: G
authors.lastname: Le Gall
authors.forename: Boyan B
authors.initials: BB
authors.lastname: Bonev
authors.forename: Melinda J
authors.initials: MJ
authors.lastname: Mayer
authors.forename: Arjan
authors.initials: A
authors.lastname: Narbad
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002236:Carbohydrate Conformation; D005798:Genes, Bacterial / Q000502:physiology; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D007778:Lactobacillus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005810:Multigene Family / Q000502:physiology; D009154:Mutation; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C083492:EPSI polysaccharide; D011135:Polysaccharides, Bacterial; D005964:Glucosyltransferases
keywords: Atomic Force Microscopy; Bacteria; Carbohydrate Structure; Exopolysaccharide; Lactobacillus johnsonii; Mutant; Nuclear Magnetic Resonance; eps Cluster
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