Structure of the O-specific polysaccharide from the lipopolysaccharide of Citrobacter gillenii O11, strain PCM 1540

The O-specific polysaccharide of the lipopolysaccharide of Citrobacter gillenii PCM 1540 (serogroup O11) consists of D-Glc, D-Man, D-GalNAc, D-GlcNAc, 2-acetamido-2,6-dideoxy-D-galactose (D-FucNAc) and O-acetyl groups in the ratios 2:1:1:1:1:1. On the basis of sugar and methylation analyses and Smith-degradation along with 1D and 2D 1H and 13C NMR spectroscopy, the following structure of the branched hexasaccharide repeating unit was established: [structure: see text]. Citrobacter werkmanii PCM 1541 belonging to the same serogroup O11 was found to have an R-form lipopolysaccharide devoid of the O-specific polysaccharide.

Structure of the O-polysaccharide of Providencia alcalifaciens O21 containing 3-formamido-3,6-dideoxy-D-galactose

The O-polysaccharide (O-antigen) of Providencia alcalifaciens O21 was obtained by mild acid degradation of the lipopolysaccharide and studied by chemical methods and NMR spectroscopy. It was found that the polysaccharide is built up of branched pentasaccharide repeating units with a terminal residue of 3-formamido-3,6-dideoxy-D-galactose (D-Fuc3NFo) and has the following structure: [structure: see text]. Anti-P. alcalifaciens O21 serum cross-reacted with the O-antigen of Proteus vulgaris O47, which contains a GalNAc trisaccharide similar to that present in the P. alcalifaciens O21 O-polysaccharide.

Role of phosphoglucomutase of Stenotrophomonas maltophilia in lipopolysaccharide biosynthesis, virulence, and antibiotic resistance

A homologue of the algC gene, responsible for the production of a phosphoglucomutase (PGM) associated with LPS and alginate biosynthesis in Pseudomonas aeruginosa, spgM, was cloned from Stenotrophomonas maltophilia. The spgM gene was shown to encode a bifunctional enzyme with both PGM and phosphomannomutase activities. Mutants lacking spgM produced less LPS than the SpgM(+) parent strain and had a tendency for shorter O polysaccharide chains. No changes in LPS chemistry were obvious as a result of the loss of spgM. Significantly, however, spgM mutants displayed a modest increase in susceptibility to several antimicrobial agents and were completely avirulent in an animal model of infection. The latter finding may relate to the resultant serum sensitivity of spgM mutants which, unlike the wild-type parent strain, were rapidly killed by human serum. These data highlight the contribution made by LPS to the antimicrobial resistance and virulence of S. maltophilia.

Characterization of Brucella abortus O-polysaccharide and core lipopolysaccharide mutants and demonstration that a complete core is required for rough vaccines to be efficient against Brucella abortus and Brucella ovis in the mouse model

Brucella abortus rough lipopolysaccharide (LPS) mutants were obtained by transposon insertion into two wbk genes (wbkA [putative glycosyltransferase; formerly rfbU] and per [perosamine synthetase]), into manB (pmm [phosphomannomutase; formerly rfbK]), and into an unassigned gene. Consistent with gene-predicted roles, electrophoretic analysis, 2-keto-3-manno-D-octulosonate measurements, and immunoblots with monoclonal antibodies to O-polysaccharide, outer and inner core epitopes showed no O-polysaccharide expression and no LPS core defects in the wbk mutants. The rough LPS of manB mutant lacked the outer core epitope and the gene was designated manB(core) to distinguish it from the wbk manB(O-Ag). The fourth gene (provisionally designated wa**) coded for a putative glycosyltransferase involved in inner core synthesis, but the mutant kept the outer core epitope. Differences in phage and polymyxin sensitivity, exposure or expression of outer membrane protein, core and lipid A epitopes, and lipid A acylation demonstrated that small changes in LPS core caused significant differences in B. abortus outer membrane topology. In mice, the mutants showed different degrees of attenuation and induced antibodies to rough LPS and outer membrane proteins. Core-defective mutants and strain RB51 were ineffective vaccines against B. abortus in mice. The mutants per and wbkA induced protection but less than the standard smooth vaccine S19, and controls suggested that anti O-polysaccharide antibodies accounted largely for the difference. Whereas no core-defective mutant was effective against B. ovis, S19, RB51, and the wbkA and per mutants afforded similar levels of protection. These results suggest that rough Brucella vaccines should carry a complete core for maximal effectiveness.

The Edwardsiella ictaluri O polysaccharide biosynthesis gene cluster and the role of O polysaccharide in resistance to normal catfish serum and catfish neutrophils

Edwardsiella ictaluri, the causative agent of enteric septicaemia of catfish (ESC), expresses long O polysaccharide (OPS) chains on its surface. The authors previously reported the construction of an isogenic Ed. ictaluri OPS mutant strain and demonstrated that this strain is avirulent in channel catfish. This paper reports the cloning of the Ed. ictaluri OPS biosynthesis gene cluster and identification of the mutated gene in the OPS-negative strain. The sequenced region contains eight complete ORFs and one incomplete ORF encoding LPS biosynthesis enzymes. The mutated gene (designated wbiT) was similar to other bacterial galactose-4-epimerases. Glycosyl composition analysis indicated that wild-type Ed. ictaluri OPS contains higher amounts of galactose and N-acetylgalactosamine than the OPS mutant strain, which correlated well with predicted functions of the genes identified in the OPS biosynthesis cluster. The OPS mutant had a relatively small, but significant, decrease in its ability to survive in normal catfish serum compared to wild-type Ed. ictaluri, but it retained the ability to resist killing by catfish neutrophils.

Structural and serological characterization of the lipopolysaccharide from Proteus penneri 20 and classification of the cross-reacting Proteus penneri strains 10, 16, 18, 20, 32 and 45 in Proteus serogroup O17

O-specific polysaccharide (O-antigen) of the lipopolysaccharide of Proteus penneri 20 was studied using sugar analysis along with various one- and two-dimensional NMR spectroscopy techniques. The following structure of the polysaccharide was established: [formula: see text] It has the same carbohydrate backbone structure as that described earlier for P. penneri 16, in which the positions of the O-acetyl groups have not been determined. P. penneri 20 O-antiserum showed a strong cross-reactivity with the lipopolysaccharides of P. penneri 10, 16, 18, 32, 45 and P. mirabilis O17. These data enable classifying these strains together with P. penneri 20 in one Proteus serogroup, O17.

Structural determination of the O-specific chain of the lipopolysaccharide from the mushrooms pathogenic bacterium Pseudomonas tolaasii

The complete structure of the O-specific polysaccharide of the lipopolysaccharide isolated from the cultivated mushrooms pathogen Pseudomonas tolaasii is described. The structural determination, achieved by chemical and spectroscopical analyses, indicates a novel tetrasaccharide repeating unit built up of two units of 2-acetamido-2,6-di-deoxy-glucopyranose (Quinovosamine, QuipNAc) and two units of 2-acetamido-2-deoxy-gulopyranuronamide (GulpNAcAN), one of which is acetylated at C-3 position:

The identity of the O-specific polysaccharide structure of Citrobacter strains from serogroups O2, O20 and O25 and immunochemical characterisation of C. youngae PCM 1507 (O2a,1b) and related strains

Serological studies using SDS-PAGE and immunoblotting revealed that from five strains that are ascribed to Citrobacter serogroup O2, four strains, PCM 1494, PCM 1495, PCM 1496 and PCM 1507, are reactive with specific anti-Citrobacter O2 serum. In contrast, strain PCM 1573 did not react with anti-Citrobacter O2 serum and, hence, does not belong to serogroup O2. The LPS of Citrobacter youngae O2a,1b (strain PCM 1507) was degraded under mild acidic conditions and the O-specific polysaccharide (OPS) released was isolated by gel chromatography. Sugar and methylation analyses along with (1)H- and (13)C-NMR spectroscopy, including two-dimensional (1)H,(1)H COSY, TOCSY, NOESY and (1)H,(13)C HSQC experiments, showed that the repeating unit of the OPS has the following structure: [structure: see text]. NMR spectroscopic studies demonstrated that Citrobacter werkmanii O20 and C. youngae O25 have the same OPS structure as C. youngae O2. Sugar and methylation analyses of the core oligosaccharide fractions demonstrated structural differences in the lipopolysaccharide core regions of these strains, which may substantiate their classification in different serogroups.

Efficient synthesis of a heptasaccharide, the repeating unit of the O-chain lipopolysaccharide produced by Xanthomonas campestris strain 642

alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->3)-[beta-D-Xylp-(1-->2)-][beta-D-Xylp-(1-->4)-]alpha-L-Rhap-(1-->3)-alpha-L-Rhap, the repeating unit of the O-chain lipopolysaccharide produced by Xanthomonas campestris strain 642 was synthesized as its methyl glycoside via 3-O-selective glycosylation of methyl alpha-L-rhamnopyranosyl-(1-->3)-2,4-di-O-benzoyl-alpha-L-rhamnopyranoside (9) with 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl-(1-->3)-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl-(1-->2)-3,4-di-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate (8), followed by dixylosylation with 2,3,4-tri-O-benzoyl-alpha,beta-D-xylopyranosyl trichloroacetimidate (12) and subsequent deacylation.

Export of O-specific lipopolysaccharide

The O antigen is the most surface-exposed component of the lipopolysaccharide (LPS) molecule and its biogenesis involves several complex mechanisms not completely well understood. All of these mechanisms involve biochemical reactions that occur on the cytoplasmic side of the plasma membrane as well as several different translocation pathways that deliver the nascent O antigens in a glycolipid form to the periplasmic side of the plasma membrane. This article discusses our current understanding of the mechanisms operating in the biogenesis of the O-specific LPS.

A unique variant of streptococcal group O-antigen (C-polysaccharide) that lacks phosphocholine

Streptococcus mitis strain SK598, which represents a subgroup of biovar 1, possesses a unique variant of the C-polysaccharide found in the cell wall of all strains of Streptococcus pneumoniae and in some strains of S. mitis. This new variant lacks the choline methyl groups in contrast to the previously characterized forms of C-polysaccharide, which all contain one or two choline residues per repeat. The following structure of the repeating unit of the SK598 polysaccharide was established: where AAT is 2-acetamido-4-amino-2,4,6-trideoxy-d-galactose. This structure is identical to the double choline-substituted form of C-polysaccharide, except that it is substituted with ethanolamine instead of choline. This extends the number of recognized C-polysaccharide variants to four.

First synthesis of beta-D-Galf-(1-->3)-D-Galp--the repeating unit of the backbone structure of the O-antigenic polysaccharide present in the lipopolysaccharide (LPS) of the genus Klebsiella

beta-D-Galactofuranosyl-(1-->3)-D-galactopyranose (1), the repeating unit of the backbone structure of the O-antigenic polysaccharide present in the lipopolysaccharide (LPS) of the genus Klebsiella, has been efficiently synthesized using 1,2:5,6-di-O-isopropylidine-alpha-D-galactofuranose (3) as the glycosyl acceptor and 2,3,5,6-tetra-O-benzoyl-beta-D-galactofuranosyl trichloroacetimidate (6) as the glycosyl donor with TMSOTf as catalyst by the well-known Schmidt glycosylation method. The preparation of 3 was improved by increasing the ratio of DMF to acetone and employing a solid-supported catalyst.

Multicopy icsA is able to suppress the virulence defect caused by the wzz(SF) mutation in Shigella flexneri

The lipopolysaccharides (LPS) of Shigella flexneri are important for virulence and their O antigen (Oag) polysaccharide chains affect IcsA (VirG)-mediated actin-based motility (ABM) within mammalian cells. S. flexneri 2a 2457T has smooth LPS whose Oag chains have two modal lengths (short (S)-type and very long (VL)-type), and has IcsA predominantly located at one pole on its cell surface. A S. flexneri 2457T wzz(SF) mutant (RMA696) has VL-type Oag but not S-type Oag chains, less IcsA detectable by immunofluorescence on its cell surface, reduced virulence and defective ABM. Introduction of a plasmid encoding IcsA into S. flexneri wzz(SF) showed that multicopy icsA could suppress the virulence defects (Sereny reaction, HeLa cell monolayer plaquing, and F-actin comet tail formation) caused by the wzz(SF) mutation suggesting that the VL-type Oag chains were masking IcsA and limiting the amount available to initiate ABM.

Lipopolysaccharide O antigen chains mask IcsA (VirG) in Shigella flexneri

Shigella flexneri 2a strain 2457T lipopolysaccharide (LPS) has O antigen (Oag) chains with two modal lengths (S-type and VL-type), and has IcsA apparently located at one pole on its cell surface. Treatment of Y serotype derivatives of 2457T and RMA696 (2457T wzz(SF)) with Sf6 tailspike protein (TSP) resulted in hydrolysis of Oag chains, and an increase in detection of IcsA by indirect immunofluorescence staining on both the lateral and polar regions of the cell surface. Newly synthesised IcsA expressed from a pBAD promoter in a S. flexneri Y strain was also detected on both the lateral and polar regions of the cell when incubated with TSP prior to immunofluorescence staining. We conclude that IcsA is actually located on both lateral and polar regions of the S. flexneri cell surface, and that LPS Oag chains mask the presence of IcsA by hindering its detection with antibodies. These results have implications for the mechanism of IcsA export. They suggest that while IcsA export is predominantly targeted to the old cell pole, it can also occur on the lateral regions of the cell surface.

Structure of the O-specific polysaccharide of Providencia rustigianii O14 containing N(epsilon)-[(S)-1-carboxyethyl]-N(alpha)-(D-galacturonoyl)-L-lysine

The O-specific polysaccharide of Providencia rustigianii O14 was obtained by mild acid degradation of the LPS and studied by chemical methods and NMR spectroscopy, including 2D 1H,(1)H COSY, TOCSY, NOESY, and 1H,(13)C HSQC experiments. The polysaccharide was found to contain N (epsilon)-[(S)-1-carboxyethyl]-N(alpha)-(D-galacturonoyl)-L-lysine ('alaninolysine', 2S,8S-AlaLys). The amino acid component was isolated by acid hydrolysis and identified by 13C NMR spectroscopy and specific optical rotation, using synthetic diastereomers for comparison. The following structure of the trisaccharide repeating unit of the polysaccharide was established:Anti-P. rustigianii O14 serum was found to cross-react with O-specific polysaccharides of Providencia and Proteus strains that contains amides of uronic acid with N(epsilon)-[(R)-1-carboxyethyl]-L-lysine and L-lysine.

Campylobacter jejuni binds intestinal H(O) antigen (Fuc alpha 1, 2Gal beta 1, 4GlcNAc), and fucosyloligosaccharides of human milk inhibit its binding and infection

The most common cause of infant mortality is diarrhea; the most common cause of bacterial diarrhea is Campylobacter jejuni, which is also the primary cause of motor neuron paralysis. The first step in campylobacter pathogenesis is adherence to intestinal mucosa. We found that such binding was inhibited in vitro by human milk and, with high avidity, by alpha1,2-fucosylated carbohydrate moieties containing the H(O) blood group epitope (Fuc alpha 1,2Gal beta 1,4GlcNAc em leader ). In studies on the mechanism of adherence, campylobacter, which normally does not bind to Chinese hamster ovary cells, bound avidly when the cells were transfected with a human alpha1,2-fucosyltransferase gene that caused overexpression of H-2 antigen; binding was specifically inhibited by H-2 ligands (lectins Ulex europaeus and Lotus tetragonolobus and H-2 monoclonal antibody), H-2 mimetics, and human milk oligosaccharides. Human milk oligosaccharides inhibited campylobacter colonization of mice in vivo and human intestinal mucosa ex vivo. Campylobacter colonization of nursing mouse pups was inhibited if their dams had been transfected with a human alpha1,2-fucosyltransferase gene that caused expression of H(O) antigen in milk. We conclude that campylobacter binding to intestinal H-2 antigen is essential for infection. Milk fucosyloligosaccharides and specific fucosyl alpha1,2-linked molecules inhibit this binding and may represent a novel class of antimicrobial agents.

New structures of the O-specific polysaccharides of Proteus. 3. Polysaccharides containing non-carbohydrate organic acids

Four new Proteus O-specific polysaccharides were isolated by mild acid degradation from the lipopolysaccharides of P. penneri 28 (1), P. vulgaris O44 (2), P. mirabilis G1 (O3) (3), and P. myxofaciens (4), and their structures were elucidated using NMR spectroscopy and chemical methods. They were found to contain non-carbohydrate organic acids, including ether-linked lactic acid and amide-linked amino acids, and the following structures of the repeating units were established: [Figure: see text], where (S)-Lac and (R)-aLys stand for (S)-1-carboxyethyl (residue of lactic acid) and N(epsilon)-[(R)-1-carboxyethyl]-L-lysine ("alaninolysine"), respectively. The data obtained in this work and earlier serve as the chemical basis for classification of the bacteria Proteus.

Environmental isolates of Citrobacter braakii that agglutinate with Escherichia coli O157 antiserum but do not possess the genes responsible for the biosynthesis of O157 somatic antigen

While searching for Escherichia coli O157 in the aquatic environment of Calcutta using an immunodetection procedure, we fortuitously detected five strains of Citrobacter braakii, which cross-reacted with the commercially available O157 polyvalent antiserum. The five C. braakii isolates gave positive results when a sensitive dot-ELISA was performed with E. coli O157 monoclonal antibody. Further, the O157 monoclonal antibody recognized the bands of proteinase K treated whole cells of lipopolysaccharide of all the C. braakii isolates. Apart from weak reactions with two or three of the DNA probes, all the C. braakii strains did not hybridize with the other probes spanning the minimum region required for O157 O-antigen biosynthesis. These strains did not possess any of the virulence genes that are commonly found in the Shiga toxin-producing E. coli (STEC) specially the serotype O157: H7. Therefore, it appears that the serological cross-reaction between C. braakii and E. coli O157 antiserum is based on structural mimicry between the O-polysaccharide of C. braakii and E. coli O157.

Genetic modulation of Shigella flexneri 2a lipopolysaccharide O antigen modal chain length reveals that it has been optimized for virulence

The lipopolysaccharide (LPS) molecules of Shigella flexneri 2a have O antigen (Oag) polysaccharides with two modal chain length distributions. The chromosomal wzz(SF) gene results in short (S) type Oag chains [11-17 Oag repeat units (RUs)], and the pHS-2 plasmid-located wzz(pHS2) gene results in very long (VL) type Oag chains (>90 Oag RUs). S. flexneri wzz(SF) mutants are unable to form plaques on HeLa cell monolayers and F-actin comet tails, indicating that IcsA/VirG function in actin-based motility (ABM) is defective. An S. flexneri wzz(SF) wzz(pHS2) double mutant had LPS with relatively short, random length Oag chains and, paradoxically, was able to form plaques and F-actin comet tails. The influence of Oag modal chain length distribution on virulence and related properties was investigated using complementation with different wzz genes. Wzz(O139) from Vibrio cholerae O139 and Wzz(ST) from Salmonella enterica serovar Typhimurium were fully functional in Shigella flexneri, resulting in LPS with either very short (VS) type Oag chains (2-7 Oag RUs) or long (L) type Oag chains (19-35 RUs), respectively. In the absence of VL-type Oag chains, the VS-, S- and L-type Oag chains were permissive for plaque and F-actin comet tail formation. However, in the presence of LPS with VL-type Oag chains, the VS- and S-type Oag chains but not the L-type Oag chains were permissive for plaque and F-actin comet tail formation. These data, and the results of a previous investigation, show that IcsA function in ABM requires LPS Oag chains with at least two but less than 18 RUs when VL-type Oag chains are co-expressed on the cell surface. However, in the absence of the VL-type Oag chains, LPS Oag chains with at least two but less than 90 RUs are able to support IcsA function in ABM. Indirect immunofluorescence staining of IcsA on the cell surface of the S. flexneri strains did not correlate with the observed effect of Oag chain length on plaque and F-actin comet tail formation. However, when intracellular bacteria lacking VL-type Oag chains were examined, an inverse correlation between Oag modal chain length and detection of IcsA was observed, i.e. staining decreased with increased modal length. It is hypothesized that Oag chains can mask IcsA and interfere with its function in ABM, and a model is presented to explain how LPS Oag and IcsA may interact. It is suggested that S. flexneri 2a has evolved to synthesize LPS with two Oag modal chain lengths, as S-type Oag chains allow IcsA to function in ABM in the presence of VL-type Oag chains that confer resistance to serum.

Synthesis of the pentasaccharide related to the repeating unit of the antigen from Shigella dysenteriae type 4 in the form of its methyl ester 2-(trimethylsilyl)ethyl glycoside

Starting from D-mannose, D-glucose and L-fucose, the pentasaccharide derivative methyl 2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl-(1-->3)-2-O-acetyl-4,6-O-benzylidene-alpha-D-mannopyranosyl-(1-->3)-2-O-acetyl-6-O-benzyl-4-O-(2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl)-alpha-D-mannopyranosyl-(1-->4)-[2-(trimethylsilyl)ethyl 2,3-di-O-benzyl-beta-D-glucopyranosid]uronate was synthesized. This compound with two alpha-mannopyranosyl units was transformed, via Walden inversion and subsequent deprotection, into the alpha-D-glucosamine-type target compound, namely methyl alpha-L-fucopyranosyl-(1-->3)-2-acetamido-2-deoxy-alpha-D-glucopyranosyl-(1-->3)-2-acetamido-2-deoxy-4-O-(alpha-L-fucopyranosyl)-alpha-D-glucopyranosyl-(1-->4)-[2-(trimethylsilyl)ethyl beta-D-glucopyranosid]uronate which is related to the repeating unit of the O-antigen from Shigella dysenteriae type 4.

Different glycosylation profile of serum IgA1 in IgA nephropathy according to the glomerular basement membrane thickness: normal versus thin

BACKGROUND

Abnormal glycosylation of immunoglobulin A1 (IgA1) has been implicated in the pathophysiological characteristics of IgA nephropathy, leading to failure of normal clearance mechanisms and mesangial deposition of serum IgA1. Furthermore, systematic measurement of glomerular basement membrane (GBM) thickness by electron microscopy evidenced two different subgroups: IgA nephropathy with normal GBM (N-GBM) and thin GBM (T-GBM). This finding prompted us to study comparatively the profile of N- and O-glycosylation of IgA1 in the two subgroups.

METHODS

Using lectin-binding properties, sialylation and galactosylation of serum IgA1, isolated on jacalin-conjugated agarose, were investigated in male and female patients with IgA nephropathy with T-GBM (n = 22) and N-GBM (n = 22) compared with matched (age and sex) healthy controls (n = 22). Sambacus nigra agglutinin (SNA) and Maackia amurensis agglutinin (MAA) were designed to examine the detection of Neu5Acalpha2,6- and Neu5Acalpha2,3-linked galactose, respectively. Helix aspersa agglutinin (HAA) was used to examine the expression of terminal N-acetylgalactosamine of the O-linked glycans in the hinge region of IgA1.

RESULTS

The following galactosylation abnormalities were confirmed in the common subgroup with N-GBM: a trend to an alpha2,6 oversialylation (SNA binding) of native IgA1 associated with a defect in its terminal galactose (HAA binding); these two findings were predominant in male patients (P < 0.05 and 0.01 for SNA and HAA, respectively). No change in MAA was observed. Conversely, no significant anomaly was found in the T-GBM variant, which could indicate the absence or low magnitude of galactosylation defects (not significant) or another yet unidentified defect.

CONCLUSION

The present study evidenced differences in glycosylation profiles of serum IgA1 according to GBM thickness (N-GBM versus T-GBM) in patients with IgA nephropathy. These data raised the possibility of different mechanisms for IgA1 glomerular deposition.

Structures and serology of the O-specific polysaccharides of bacteria of the genus Citrobacter

The review presents the structures of the O-specific polysaccharides (O-antigens) of the lipopolysaccharides isolated from over 25 Citrobacter strains, which represent different species and serogroups. The correlation between O-antigen structure and immunospecificity as well as numerous cross-reactions between Citrobacter and other enterobacterial species are discussed.

The structure of the O-specific polysaccharide chain of the Shewanella algae BrY lipopolysaccharide

An acidic O-specific polysaccharide was obtained by mild acid degradation of the Shewanella algae strain BrY lipopolysaccharide and was found to contain L-rhamnose, 2-acetamido-4-[D-3-hydroxybutyramido)]-2,4,6-trideoxy-D-glucose (D-BacNAc4NHbu), and 2-amino-2,6-dideoxy-L-galactose, N-acylated by the 4-carboxyl group of L-malic acid (L-malyl-(4-->2)-alpha-L-FucN) in the ratio 2:1:1. 1H and 13C NMR spectroscopy was applied to the intact polysaccharide, and the following structure of the repeating unit was established:-3)-alpha-D-BacNAc4NHbu-(1-->3)-alpha-L-Rha-(1-->2)-alpha-L-Rha-(1-->2)-L-malyl-(4-->2)-alpha-L-FucN-(1-. The repeating unit includes linkage via the residue of malic acid, reported here for the first time as a component of bacterial polysaccharides.

Structure of the O-specific polysaccharide of Proteus vulgaris O45 containing 3-acetamido-3,6-dideoxy-D-galactose

An O-specific polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Proteus vulgaris O45 and studied by sugar and methylation analyses along with 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, ROESY, H-detected 1H,13C HSQC and HMBC experiments. The following structure of the pentasaccharide repeating unit of the polysaccharide was established:-->6)-alpha-D-GlcpNAc-(1-->4)-alpha-D-GalpNAc-(1-->4)-alpha-D-GalpA-(1-->3)-beta-D-GlcpNAc-(1-->2)-beta-D-Fucp3NAc4Ac-(1-->where Fuc3NAc4Ac is 3-acetamido-4-O-acetyl-3,6-dideoxygalactose. A cross-reactivity of anti-P. vulgaris O45 serum was observed with several other Proteus lipopolysaccharides, which contains Fuc3N derivatives.

Lack of polymorphism in a Vibrio cholerae O139-specific DNA region encoding the somatic antigen in strains isolated during 1993-1998

Vibrio cholerae O139 Bengal emerged as a second aetiologic agent of cholera in South Asia in late 1992. This new serogroup arose from a Vibrio cholerae O1 strain by deletion of the chromosomal region encoding O1 specificity and acquisition of a novel 35-kb region encoding the O139 specificity. Previous studies indicated significant phenotypic and genotypic changes in O139 isolates over the years since its first appearance. This prompted us to study possible polymorphism in the 35-kb novel region encoding the O139 specificity. A total of 17 V. cholerae O139 isolates originating from different countries and years in South Asia and China, and a single unrelated V. cholerae O139 isolate from Argentina were studied. The 35-kb chromosomal region was amplified as two fragments of 12 and 23 kb in an extended PCR from all isolates. These amplicons were then treated separately with seven different restriction enzymes and separated by agarose gel electrophoresis. The South Asian and Chinese isolates gave identical patterns for the same enzymes, but different patterns for different enzymes, thus exhibiting no polymorphism in the 35-kb region. However, the Argentine isolate gave distinct patterns for most of the enzymes confirming its different origin. This data indicated that the portion of the chromosome encoding the O139 antigen specificity is highly conserved. As found in previous studies, the early O139 isolates were resistant to trimethoprim-sulfamethoxazole (TMP-SMX) and vibriostatic compound, O/129, and CAMP- haemolysin positive. The isolates of later years diverged exhibiting different patterns by pulsed-field gel electrophoresis (PFGE), and becoming susceptible to TMP-SMX and O/129, and CAMP-haemolysin negative.