Lipopolysaccharide isolated from a new O-antigenic form (O13) of Vibrio parahaemolyticus

Identification of four secondary acyltransferases for lipid A biosynthesis in Vibrio parahaemolyticus

In this study, four genes encoding secondary acyltransferases of lipid A in Vibrio parahaemolyticus ATCC33846 were identified. When the four genes were overexpressed in Escherichia coli MLK1067 that which produces the penta-acylated lipid A lacking the secondary acylation at the C3' position, a C_12:0 secondary acyl chain was added at the C3' position of lipid A only in E. coli overexpressing VP_RS01045, but not VP_RS00880, VP_RS08405, or VP_RS12170. When the four genes were overexpressed in E. coli MKV15b that produces lipid IV_A , a C_12:0 secondary acyl chain was again added at the C3' position in E. coli overexpressing VP_RS01045, but a C_14:0 secondary acyl chain was added at the C2' position of lipid A in E. coli overexpressing VP_RS00880, VP_RS08405, or VP_RS12170. The results indicate that four acyltransferases of lipid A are encoded by VP_RS01045, VP_RS00880, VP_RS08405, or VP_RS12170 in V. parahaemolyticus. The acyltransferase encoded by VP_RS01045 adds a C_12:0 secondary acyl chain at the C3' position of lipid A, whereas the acyltransferase encoded by VP_RS00880, VP_RS08405, or VP_RS12170 adds a C_14:0 secondary acyl chain at the C2' position of lipid A. This work contributes to understanding the biosynthetic pathway of lipid A in V. parahaemolyticus.

Structural studies of a polysaccharide from Vibrio parahaemolyticus strain AN-16000

The structure of a polysaccharide from Vibrio parahaemolyticus strain AN-16000 has been investigated. The sugar and absolute configuration analysis revealed d-Glc, d-GalN, d-QuiN and l-FucN as major components. The PS was subjected to dephosphorylation with aqueous 40% HF to obtain an oligosaccharide that was analyzed by (1)H and (13)C NMR spectroscopy. The HR-MS spectrum of the oligosaccharide revealed a pentasaccharide composed of two Glc residues, one QuiNAc and one GalNAc, one FucNAc, as well as a glycerol moiety. The structure of the PS was determined using (1)H, (13)C, (15)N and (31)P NMR spectroscopy; inter-residue correlations were identified by (1)H,(13)C-heteronuclear multiple-bond correlation, (1)H,(1)H-NOESY and (1)H,(31)P-hetero-TOCSY experiments. The PS backbone has the following teichoic acid-like structure: →3)-d-Gro-(1-P-6)-β-d-Glcp-(1→4)-α-l-FucpNAc-(1→3)-β-d-QuipNAc-(1→ with a side-chain consisting of α-d-Glcp-(1→6)-α-d-GalpNAc-(1→ linked to the O3 position of the FucNAc residue.

Characterization of the carbohydrate backbone of Vibrio parahaemolyticus O6 lipopolysaccharides

Structural characterization studies have been carried out on the carbohydrate backbone of Vibrio parahaemolyticus serotype O6 lipopolysaccharides (LPS). The carbohydrate backbone isolated from O6 LPS by sequential derivatization, that is, dephosphorylation, O-deacylation, pyridylamination, N-deacylation and N-acetylation, is a nonasaccharide consisting of 3 mol of D-glucosamine (GlcN) (of which one is pyridylaminated), 2 mol of L-glycero-D-manno-heptose (Hep), and 1 mol each of D-galactose (Gal), D-glucose (Glc), D-glucuronic acid (GlcA) and 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo). Structural analyses by nuclear magnetic resonance spectroscopy and fast-atom bombardment mass spectrometry demonstrated that the carbohydrate backbone is β-Galp-(1→2)-α-Hepp-(1→3)-α-Hepp-(1→5)-α-Kdop-(2→6)-β-GlcpNAc-(1→6)-GlcNAc-PA, in which the 3-substituted α-Hepp is further substituted by β-GlcpNAc-(1→4)-β-Glcp at position 4 and by β-GlcpA at position 2. In native O6 LPS, an additional 1 mol of D-galacturonic acid, which is liberated by dephosphorylation in hydrofluoric acid, is present at an unknown position. A previous study by the present authors reported that, of 13 O-serotype LPS of V. parahaemolyticus, the only LPS from which Kdo was detected was from O6 LPS after mild acid hydrolysis. In the present study, we have demonstrated that only 1 mol of Kdo is present at the lipid A proximal position, a component which is common to the LPS in all serotypes of the bacterium, and that there is no additional Kdo in the carbohydrate backbone of O6 LPS. ELISA and ELISA inhibition analysis using antisera against O6 and Salmonella enterica Minnesota R595 and LPS of both strains further revealed that Kdo is not involved as an antigenic determinant of O6 LPS.

Structural analysis of the carbohydrate backbone of Vibrio parahaemolyticus O2 lipopolysaccharides

A structural investigation has been carried out on the carbohydrate backbone of Vibrio parahaemolyticus O2 lipopolysaccharides (LPS) isolated by dephosphorylation, O-deacylation and N-deacylation. The carbohydrate backbone is a short-chain saccharide consisting of nine monosaccharide units i.e., 1 mol each of D-galactose (Gal), D-glucose (Glc), D-glucuronic acid (GlcA), L-glycero-D-manno-heptose (L,D-Hep), D-glycero-D-manno-heptose (D,D-Hep), 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo), 5,7-diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulosonic acid (NonlA), and 2 mol of 2-amino-2-deoxy-D-glucose (D-glucosamine, GlcN). Based on the data obtained by NMR spectroscopy, fast-atom bombardment mass spectrometry (FABMS) and methylation analysis, a structure was elucidated for the carbohydrate backbone of O2 LPS. In the native O2 LPS, the 2-amino-2-deoxy-D-glucitol (GlcN-ol) at the reducing end of the nonasaccharide is present as GlcN. The lipid A backbone is a beta-D-GlcN-(1-->6)-D-GlcN disaccharide as is the case for many Gram-negative bacterial LPS. The lipid A proximal Kdo is substituted by the distal part of the carbohydrate chain at position-5. In the native O2 LPS, D-galacturonic acid, which is liberated from LPS by mild acid treatment or by dephosphorylation in hydrofluoric acid, is present although its binding position is unknown at present.

Structure and serological characterization of 5,7-diamino-3,5,7,9-tetradeoxy-non-2-ulosonic acid isolated from lipopolysaccharides of Vibrio parahaemolyticus O2 and O-untypable strain KX-V212

Lipopolysaccharides (LPS) of Vibrio parahaemolyticus O2 and O-untypable (OUT) strain (KX-V212) isolated from an individual patient were shown to contain 5,7-diamino-3,5,7,9-tetradeoxy-non-2-ulosonic acid (NonlA), which was readily released from LPS by mild acid hydrolysis. In the present study, we investigated the chemical and serological properties of NonlA isolated from LPS of V. parahaemolyticus O2 and OUT KX-V212. GC-MS and NMR analysis identified the NonlA from LPS of O2 to be 5,7-diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulosonic acid (5NAc7NAcNonlA) and that from LPS of KX-V212 to be 5-acetamido-7-(N-acetyl-D-alanyl)amido-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulosonic acid (5NAc7NAlaNAcNonlA). In ELISA inhibition analysis, 5NAc7NAcNonlA inhibited the O2 LPS/anti-O2 antiserum system, whereas, 5NAc7NAlaNAcNonlA did not show any inhibitory activity. However, after N-deacylation of 5NAc7NAlaNAcNonlA followed by N-acetylation, the product (5NAc7NAcNonlA) inhibited the O2 LPS/anti-O2 antiserum system to the same extent as that of 5NAc7NAcNonlA obtained from O2 LPS. These results suggest that 5NAc7NAcNonlA might be related to the serological specificity of O2 LPS as one of main epitope(s) involved in O2 LPS.

Chemical and serological properties of lipopolysaccharides from Vibrio parahaemolyticus O-untypeable strains isolated from patients

Chemical and serological studies have been carried out on the O-antigenic lipopolysaccharides (LPS) of six strains, U-6443, W-90144, X-3972, AD-7999, 90A-6611 and KX-V212, of Vibrio parahaemolyticus isolated from patients. The O-serotypes of these strains have not been identified because they were not agglutinated by any diagnostic antisera against known O-serotype strains. A compositional sugar analysis of their LPS revealed that out of the six O-untypeable (OUT) strains, U-6443, W-90144 and AD-7999 strains belonged to chemotype II (chemotype of O2), 90A-6611 and KX-V212 strains to chemotype III (chemotype of O3, O5, O11 and O13) and X-3972 strain to chemotype IV (chemotype of O4). A structural analysis of LPS isolated from KX-V212 revealed that the inner core region of the LPS consisted of only one mole of 2-keto-3-deoxy-D-manno-octonic acid, which carried a phosphate group at position C4 and the outer core at position C5. In passive hemolysis tests performed by using LPS as the antigen to sensitize sheep red blood cells (SRBC), and diagnostic antisera (O1 to O11) or anti-whole-cell rabbit antisera raised against O12, O13 and the six OUT strains, strong cross-reactivity was observed among LPS derived from the strains belonging to chemotype II (U-6443, W-90144, AD-7999 and O2). Strong cross-reactivity was also observed between X-3972 (chemotype IV) and O4 LPS. In contrast, LPS from two of the strains belonging to chemotype III (90A-6611 and KX-V212) did not react with any of the antisera raised against known O-serotypes. Cross-absorption tests showed that the O-antigens of U-6443, W-90144 and AD-7999 were identical to that of O2, and the O-antigen of X-3972 to that of O4. On the other hand, after the absorption of antisera raised against 90A-6611 and KX-V212 with O2 cells, the hemolytic activities against SRBC sensitized with homologous LPS were still retained at a high titer, whereas the hemolytic activities against SRBC sensitized with LPS from other O-serotype strains were completely eliminated. A cross-absorption test revealed that the O-antigens of these two strains were identical to each other. Thus, it was demonstrated that the O-serotype of OUT strains 90A-6611 and KX-V212 was not involved in the known O-serotypes; rather it represented a novel serotype which has not hitherto been reported.

Vibrio parahaemolyticus O serotypes from O1 to O13 all produce R-type lipopolysaccharide: SDS-PAGE and compositional sugar analysis

The molecular architecture of lipopolysaccharide (LPS) isolated from all O serotypes of Vibrio parahaemolyticus was investigated. In gel chromatography on a Sephadex G-50 column, the degraded polysaccharide fraction prepared from each serotype LPS by mild acid hydrolysis yielded only core oligosaccharide (Frc II) and monosaccharide (Frc III) fractions, but no fraction (Frc I) corresponding to O polysaccharide chain consisting of polymeric repeating oligosaccharide units. Compositional sugar analysis of Frc II and III suggested that the sugar chain of LPS of all the serotypes of V. parahaemolyticus consisted of at most ten monosaccharides. Sodium dodecylsulfate-polyacrylamide gel electrophoresis of the LPS resulted in no doublet ladder band similar to that observed for S-type enterobacterial LPS. These results are compatible with the interpretation that V. parahaemolyticus O serotypes from O1 to O13 all produce R-type LPS, despite the morphologically smooth appearance, demonstrated virulence and serological O-specificity.