Occurrence of 2,4-dihydroxy-3,3,4-trimethylpyroglutamic acid as an N-acyl substituent in the O-polysaccharide chain of the lipopolysaccharide of Vibrio anguillarum V-123

Genetic analysis of genes involved in synthesis of modified 4-amino-4,6-dideoxyglucose in flagellin of Pseudomonas syringae pv. tabaci

Glycosylation of flagellin contributes to swimming and swarming motilities, adhesion ability, and consequently virulence in Pseudomonas syringae pv. tabaci 6605. Glycans attached to six serine residues are located in the central region of the flagellin polypeptide. The glycan structure at position Ser 201 was recently revealed to consist of two L-rhamnoses and one modified 4-amino-4,6-dideoxyglucose (viosamine). To clarify the mechanisms for glycosylation of modified viosamine, genes encoding dTDP-viosamine aminotransferase (vioA), dTDP-viosamine acetyltransferase (vioB), and viosamine-derivative transferase (vioT) were isolated and defective mutants were generated. MALDI-TOF-MS analysis of a lysyl endopeptidase-digested peptide including all six glycosylation sites from each flagellin indicated that the molecular masses of the three flagellin mutants were reduced with highly heterogeneous patterns at regular intervals of 146 Da in the mass range from m/z 13,819 to 15,732. The data indicated that the glycopeptides obtained from mutants had glycans consisting only of deoxyhexose instead of the flagellin glycans including the viosamine derivatives determined previously. The motility and virulence on host tobacco leaves were strongly impaired in the Delta vioA mutant and were weakly reduced in the Delta vioB and Delta vioT mutant strains. These results suggest that the genes vioA, vioB, and vioT are essential for glycosylation of flagellin, and accordingly are required for bacterial virulence.

Structural elucidation of a novel core oligosaccharide backbone of the lipopolysaccharide from the new bacterial species Agrobacterium larrymoorei

Agrobacterium larrymoorei is a Gram-negative phytopathogenic bacterium, which produces tumours on Ficus benjamina plants and differs from other Agrobacteria both genetically and biochemically. The lipopolysaccharide (LPS) plays an important role in the pathogenesis of Agrobacteria. The present paper is the first report on the molecular primary structure of the core region of an Agrobacterium LPS. The following structure of the core and lipid A carbohydrate backbone of an R-form LPS of A. larrymoorei was determined by chemical degradations and 1D and 2D NMR spectroscopy: [carbohydrate structure: see text] All sugars are alpha-D-pyranoses if not stated otherwise, Kdo is 3-deoxy-D-manno-oct-2-ulosonic acid, Qui3NAcyl is 3,6-dideoxy-3-(3-hydroxy-2,3-dimethyl-5-oxoprolylamino)glucose, GlcAN and GalAN are amides of GlcA and GalA.

Somatic antigens of pseudomonads: structure of the O-specific polysaccharide of Pseudomonas fluorescens IMV 2366 (biovar C)

The O-specific polysaccharide of P. fluorescens IMV 2366 was studied by sugar and methylation analyses along with 1H and 13C NMR spectroscopy, including 2D gsCOSY, TOCSY, gsNOESY, H-detected 1H,(13)C gsHSQC, HMQC-TOCSY, and gsHMBC experiments. The polysaccharide contains L-rhamnose, 2-acetamido-2,6-dideoxy-D-galactose (D-FucNAc) and 3-acylamido-3,6-dideoxy-D-glucose (D-Qui3NAcyl, where Acyl is 3-hydroxy-2,3-dimethyl-5-oxoprolyl). The structure 1 of the polysaccharide was found to be similar to the structure 2 of a 6-deoxy-L-talose (L-6dTal)-containing O-specific polysaccharide of a non-classified P. fluorescens strain, 361, studied earlier [Khomenko, V. A.; Naberezhnykh, G. A.; Isakov, V. V.; Solov'eva, T. F.; Ovodov, Y. S.; Knirel, Y. A.; Vinogradov, E. V. Bioorg. Khim. 1986, 12, 1641-1648; Naberezhnykh, G. A.; Khomenko, V. A.; Isakov, V. V., El'kin, Y. N.; Solov'eva, T. F.; Ovodov, Y. S. Bioorg. Khim. 1987, 13, 1428-1429]. --> 2)-beta-D-Quip3NAcyl-(1 --> 3)-alpha-L-Rhap-(1 --> 3)-alpha-D-FucpNAc-(1 --> 1. --> 4)-beta-D-Quip3NAcyl-(1 --> 3)-alpha-L-6dTalp4Ac-(1 --> 3)-alpha-D-FucpNAc-(1 -->2.

Structural studies of the lipopolysaccharide O-antigen and capsular polysaccharide of Vibrio anguillarum serotype O:2

Vibriosis caused by Vibrio anguillarum affects salmonid and marine fish species worldwide and is considered to be one of the most serious threats to the success of commercial fish farming. In the course of this study, it was found that V. anguillarum serotype O:2 strains produce an acidic capsular polysaccharide having the identical structure to that of the O-chain polysaccharide. One-dimensional and two-dimensional nuclear magnetic resonance techniques, together with partial hydrolysis and various specific modifications, were used to determine the structure of these polysaccharides. It is proposed that both O-chain and capsular polysaccharide of V. anguillarum serotype O:2 are composed of linear tetrasaccharide repeating units having the following structure, in which Glc2NAc3NAN represents 2-acetamido-3-amino-2,3-dideoxy-D-glucuronamide, Man2NAc3AmA is 3-acetamidino-2-acetamido-2,3-dideoxy-D-mannuronic acid. Am represents an acetamidino group, Gal(NAc)2A is 2,3-diacetamido-2,3-dideoxy-L-galacturonic acid, Bac(NAc)2 is 2,4-diacetamido-2,4,6-trideoxy-D-glucose (N,N'-diacetylbacillosamine) and Fo is formyl.

Structural studies of the Vibrio cholerae O:5 O-antigen polysaccharide

The O-polysaccharide from Vibrio cholerae O:5 has been investigated, using NMR spectroscopy as the main method. Fast atom bombardment mass spectrometry (FABMS) studies of fragments obtained on treatment with anhydrous hydrogen fluoride or methanolic hydrogen chloride gave further structural information. Some structural features were also determined by comparison of nuclear Overhauser enhancement (NOE) contacts with calculated H-H distance in different oligosaccharide models. It is concluded that the O-polysaccharide has the following structure, in which D-Qui p NAc4NAc is 2,4-diacetamido-2,4,6-trideoxy-D-glucose, and D-Fuc p 3NX is 3-amino-3,6-dideoxy-D-galactose acylated with a (R,R)-3-hydroxy-3-methyl-5-oxoproline group. [formula: see text]

Characterization of a novel chromosomal virulence locus involved in expression of a major surface flagellar sheath antigen of the fish pathogen Vibrio anguillarum

The fish pathogenic bacterium Vibrio anguillarum 775.17B was mutated by the use of transposon Tn5-132. Two hundred independent exconjugants were isolated and screened for a reduction of virulence in experimental infections of rainbow trout (Onchorhynchus mykiss). Two of these exconjugants, VAN20 and VAN70, showed a significant reduction in virulence after both intraperitoneal and immersion infections. The avirulent mutants showed no loss of any previously suggested virulence determinants of V. anguillarum. One of the mutants (VAN70) was further characterized. DNA sequence analysis revealed two open reading frames, the gene into which Tn5-132 had been inserted (virA) and a closely linked upstream gene (virB). A virB mutant of 775.17B, NQ706, was isolated and also shown to be avirulent. The deduced amino acid sequences of virA and virB correspond to proteins with molecular weights of 36,000 and 42,000, respectively. Insertional mutagenesis of the corresponding virA and virB genes of a clinical isolate of V. anguillarum, serotype O1, also resulted in avirulence. In immunoblot experiments, the total cell lysates of VAN70 (virA) and NQ706 (virB) did not respond to a rabbit polyclonal antiserum directed against whole cells of 775.17B (wild type). This suggests that virA and virB are involved in the biosynthesis of a major surface antigen important for the virulence of V. anguillarum. Immunogold electron microscopy showed that a constituent of the flagellar sheath was expressed by 775.17B (wild type) but not by VAN70 (virA) and NQ706 (virB), suggesting that the major surface antigen lacking in VAN70 and NQ706 is located on the outer sheath of the flagellum. Analysis of this major surface antigen revealed it likely to be lipopolysaccharide. Further analysis showed that the flagellum and the major surface antigen were expressed in vivo during fish infections.

Structure of the O-polysaccharide chain of the lipopolysaccharide of Vibrio anguillarum V-123

The O-polysaccharide chain (PS-1), released by mild acidic treatment of the LPS of V. anguillarum V-123 (serogroup JO-2), a pathogenic bacterium of marine and estuarine fish, consists of 2-amino-2-deoxy-D-galacturonic acid, 2-amino-2,6-dideoxy-D-glucose (D-quinovosamine), and 4-amino-4,6-dideoxy-D-glucose (D-viosamine) N-acylated with 2,4-dihydroxy-3,3,4-trimethylpyroglutamic acid. Strong-acid hydrolysis of PS-1 afforded alpha-GalNA-(1----4)-alpha-GalNA-(1----3)-QuiN (A1) and alpha-GalNA-(1----3)-QuiN (A2), and hydrolysis with hydrogen fluoride gave N-acetylated A1 and 4-amino-4,6-dideoxy-D-glucose N-acylated by 2,4-dihydroxy-3,3,4-trimethylpyroglutamic acid. Mild treatment of PS-1 with alkali removed the N-formyl substituents and Smith degradation of the product gave alpha-QuiNAc-(1----3)-beta-VioNAcyl-(1----3)-alpha-GalNAc A-(1----3)-2,3,4- trihydroxybutanoic acid (S1) and S2 in which the carboxyl group of the GalNAcA residue was amidated. Thus, the repeating unit of the O-polysaccharide is----3)-alpha-GalNAcA(amino)-(1----4)-alpha-GalNFoA-(1----3 )- alpha-QuiNAc-(1----3)-beta-VioNAcyl-(1----in which the N-Acyl group is 2,4-dihydroxy-3,3,4-trimethylpyroglutamic acid and Fo is formyl.