Structural characterization of the O-polysaccharide antigen of Edwardsiella tarda MT 108

Structural analysis of Edwardsiella tarda PCM 1155 O-polysaccharide revealed the presence of unique β-L-RhapNAc3NAc derivative

The chemical structure of the lipopolysaccharide O-polysaccharide repeating unit of Edwardsiella tarda strain PCM 1155 was studied for the first time. The complete structure of repeating unit was investigated by chemical methods, ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, and matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The rarely occurring monosaccharide, 2,3-diacetamido-2,3,6-trideoxy-l-mannose (L-RhapNAc3NAc) was identified. The following structure was established.

The Complete Structure of the Core Oligosaccharide from Edwardsiella tarda EIB 202 Lipopolysaccharide

The chemical structure and genomics of the lipopolysaccharide (LPS) core oligosaccharide of pathogenic Edwardsiella tarda strain EIB 202 were studied for the first time. The complete gene assignment for all LPS core biosynthesis gene functions was acquired. The complete structure of core oligosaccharide was investigated by ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry MSⁿ, and matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry. The following structure of the undecasaccharide was established: The heterogeneous appearance of the core oligosaccharide structure was due to the partial lack of β-d-Galp and the replacement of α-d-GlcpNAcGly by α-d-GlcpNGly. The glycine location was identified by mass spectrometry.

Structure of the O-polysaccharide of Edwardsiella tarda PCM 1156

Mild acid degradation of the lipopolysaccharide of Edwardsiella tarda PCM 1156 afforded an O-polysaccharide, which was isolated by gel-permeation chromatography on Sephadex G-50 and studied by sugar and methylation analyses along with (1)H NMR and (13)C NMR spectroscopy, including 2D (1)H,(1)H COSY, TOCSY, ROESY, (1)H,(13)C HSQC, and HMBC experiments. The following structure of the linear tetrasaccharide repeating unit of the O-polysaccharide was established: [structure: see text].

Pathogenesis of and strategies for preventing Edwardsiella tarda infection in fish

Edwardsiella tarda is one of the serious fish pathogens, infecting both cultured and wild fish species. Research on edwardsiellosis has revealed that E. tarda has a broad host range and geographic distribution, and contains important virulence factors that enhance bacterial survival and pathogenesis in hosts. Although recent progress in edwardsiellosis research has enabled the development of numerous, highly effective vaccine candidates, these efforts have not been translated into a commercialized vaccine. The present review aims to provide an overview of the identification, pathology, diagnosis and virulence factors of E. tarda in fish, and describe recent strategies for developing vaccines against edwardsiellosis. The hope is that this presentation will be useful not only from the standpoint of understanding the pathogenesis of E. tarda, but also from the perspective of facilitating the development of effective vaccines.

Structures of a unique O-polysaccharide of Edwardsiella tarda PCM 1153 containing an amide of galacturonic acid with 2-aminopropane-1,3-diol and an abequose-containing O-polysaccharide shared by E. tarda PCM 1145, PCM 1151 and PCM 1158

Lipopolysaccharides of four strains of Edwardsiella tarda were degraded by mild acid hydrolysis, and the released O-polysaccharides were isolated by GPC and studied by sugar and methylation analyses along with (1)H and (13)C NMR spectroscopy, including 2D (1)H, (1)H COSY, TOCSY, ROESY, (1)H, (13)C HMBC, HSQC and HSQC-TOCSY experiments. The O-polysaccharide from E. tarda PCM 1153 was found to contain D-GalA, D-GlcNAc, D-Gal and 2-amino-1,3-propanediol (GroN). In the tetrasaccharide repeating unit, GroN is amide-linked to one of the GalA residues, and Gal is non-stoichiometrically 2- or 3-O-acetylated (~45% at each position): [structure: see text]. Three other E. tarda strains examined (PCM 1145, PCM 1151 and PCM 1158) share the following O-polysaccharide structure: [structure: see text] where Abe indicates 3,6-dideoxy-D-xylo-hexose (abequose). This structure resembles those of Citrobacter freundii O22 (PCM 1555) and Salmonella enterica O4. In accordance with the structural data, SDS-PAGE and immunoblotting of the lipopolysaccharides with anti-C. freundii O22 serum demonstrated that the O-antigens of the three E. tarda strains are serologically identical to each other and to the O-antigens of C. freundii O22 and S. enterica O4.

Characterization of Edwardsiella tarda waaL: roles in lipopolysaccharide biosynthesis, stress adaptation, and virulence toward fish

Edwardsiella tarda is the causative agent of edwardsiellosis in fish. The genome sequence of a virulent strain EIB202 has been determined. According to the genome sequence, the lipopolysaccharide (LPS) synthesis cluster containing a putative O-antigen ligase gene waaL was identified. Here, the in-frame deletion mutant ΔwaaL was constructed to analyze the function of WaaL in E. tarda EIB202. The ΔwaaL mutant displayed absence in O-antigen side chains in the LPS production. The ΔwaaL mutant exhibited an increased sensitivity to hydrogen peroxide indicating that the LPS was involved in the endurance to the oxidative stress in hosts during infection. In addition, the resistance of ΔwaaL to serum and polymyxin B decreased remarkably. The ΔwaaL mutant was also attenuated in virulence, showed an impaired ability in internalization of epithelioma papulosum cyprinid (EPC) cells and a comparatively poor ability of proliferation in vivo, which was in line with the increased LD(50) value. These results indicated that waaL gene was a functional member of the gene cluster involved in LPS synthesis and highlighted the importance of the O-antigen side chains to stress adaption and virulence in E. tarda, signifying the gene as a potential target for live attenuated vaccine against this bacterium.

Structural investigation of bacterial lipopolysaccharides by mass spectrometry and tandem mass spectrometry

Mass spectrometric studies are now playing a leading role in the elucidation of lipopolysaccharide (LPS) structures through the characterization of antigenic polysaccharides, core oligosaccharides and lipid A components including LPS genetic modifications. The conventional MS and MS/MS analyses together with CID fragmentation provide additional structural information complementary to the previous analytical experiments, and thus contribute to an integrated strategy for the simultaneous characterization and correct sequencing of the carbohydrate moiety.

Structural elucidation of the O-antigenic polysaccharide from enterohemorrhagic (EHEC) Escherichia coli O48:H21

The structure of the antigenic O-polysaccharide (O-PS) of the lipopolysaccharide (LPS) produced by the enterohemorrhagic strain of Escherichia coli O48:H21 (EHEC) has been elucidated. The O-PS obtained by mild acid hydrolysis of the LPS had [alpha]D +95 (water) and was composed of L-rhamnose (L-Rha), D-galactose (D-Gal), 2-amino-2-deoxy-D-glucose (D-GlcN), 2-amino-2-deoxy-D-galactose (D-GalN), and D-galacturonic acid (D-GalA) (1:1:1:1:1). From the results of methylation analysis, mass spectrometry, 2D NMR, and DOC-PAGE, the O-PS was shown to be a high molecular mass polymer of a repeating pentasaccharide unit having the structure: [structure: see text]. The D-Gal pA non-reducing end groups in the O-PS were partially O-acetylated (approximately 30%) at the O-2 and O-3 positions and the degree of acetylation was variable from batch to batch cell production.

Identification and characterization of the unique N-linked glycan common to the flagellins and S-layer glycoprotein of Methanococcus voltae

The flagellum of Methanococcus voltae is composed of four structural flagellin proteins FlaA, FlaB1, FlaB2, and FlaB3. These proteins possess a total of 15 potential N-linked sequons (NX(S/T)) and show a mass shift on an SDS-polyacrylamide gel indicating significant post-translational modification. We describe here the structural characterization of the flagellin glycan from M. voltae using mass spectrometry to examine the proteolytic digests of the flagellin proteins in combination with NMR analysis of the purified glycan using a sensitive, cryogenically cooled probe. Nano-liquid chromatography-tandem mass spectrometry analysis of the proteolytic digests of the flagellin proteins revealed that they are post-translationally modified with a novel N-linked trisaccharide of mass 779 Da that is composed of three sugar residues with masses of 318, 258, and 203 Da, respectively. In every instance the glycan is attached to the peptide through the asparagine residue of a typical N-linked sequon. The glycan modification has been observed on 14 of the 15 sequon sites present on the four flagellin structural proteins. The novel glycan structure elucidated by NMR analysis was shown to be a trisaccharide composed of beta-ManpNAcA6Thr-(1-4)-beta-Glc-pNAc3NAcA-(1-3)-beta-GlcpNAc linked to Asn. In addition, the same trisaccharide was identified on a tryptic peptide of the S-layer protein from this organism implicating a common N-linked glycosylation pathway.