Structures of the O4 and O18 antigens of Stenotrophomonas maltophilia: a case of enantiomeric repeating units.

The O-specific side-chain polymers of lipopolysaccharides from the reference strains for Stenotrophomonas maltophilia serogroups 04 and O18 are both xylosylated rhamnans. In the 04 polymer, both sugar components are the D isomers, whereas the O18 polymer contains only the L isomers. By means of NMR spectroscopy, methylation analysis and Smith degradation, the repeating unit of the 04 polymer was identified as a doubly-branched pentasaccharide of the structure shown below. The O18 polymer is based on the enantiomeric pentasaccharide, but the xylosyl substituent at the 4-position is apparently absent from some units. The polymers closely resemble the O antigens found in Xanthomonas campestris pathovars. [structure: see text]

Structure of the O16 antigen of Stenotrophomonas maltophilia.

A polysaccharide containing D-ribose, N-acetyl-D-glucosamine, and N-acetyl-D-mannosamine was isolated from the phenol-soluble lipopolysaccharide extracted from defatted cell walls of the reference strain (560) for serogroup O16 of Stenotrophomonas maltophilia. The results of methylation analysis, chemical degradations, and NMR spectroscopy showed that the polysaccharide is based on a branched trisaccharide repeating-unit of the structure shown below. Although ribose was absent from about half of the units in the isolated polymer, the regularity and spacing of the ladder observed on SDS-PAGE of the parent lipopolysaccharide indicate that this was an artefact of the mild acid hydrolysis used to release the polymer. On the other hand, the effects of mild alkaline hydrolysis on the polymer indicated partial O-acetylation. [structure: see text]

Structure of the acidic microcapsular glycan from the reference strain (C.D.C. 6320-58) for Serratia marcescens serotype O14:K12.

The acidic polysaccharide from Serratia marcescens serogroup O14:K12 was analyzed by means of chemical studies and NMR spectroscopy and its repeating unit structure found to be carbohydrate sequence [see text] O-Acetyl groups are proposed to be present in non-stoichiometric amounts on O-6 on one of the hexose residues in the main chain.

Structures of the O21 and O25 antigens of Stenotrophomonas maltophilia.

The O-specific side-chain polymers from Stenotrophomonas maltophilia serogroups O21 and O25 were isolated from the lipopolysaccharides of the reference strains. The O21 polymer contained D-arabinose, 2-amino-2-deoxy-D-glucose and 2-amino-2-deoxy-D-galactose in equal proportions. Methylation analysis and NMR spectroscopy showed that the polysaccharide is based on a branched trisaccharide repeating unit of the structure shown below. The O25 polymer is linear with a disaccharide repeating unit identical to that forming the backbone of the O21 polymer.

Structure of the O-specific polysaccharide for Acinetobacter baumannii serogroup O1.

A polymeric fraction containing D-galactose, N-acetyl-D-galactosamine, and N-acetyl-D-glucosamine was isolated from the lipopolysaccharide produced by the reference strain for Acinetobacter baumannii serogroup O1. By means of NMR spectroscopy, methylation analysis, and chemical degradation, the repeating unit of the polymer was identified as a branched trisaccharide of the following structure. [formula: see text].

The O7 antigen of Stenotrophomonas maltophilia is a linear D-rhamnan with a trisaccharide repeating unit that is also present in polymers for some Pseudomonas and Burkholderia species.

The O antigen polymer recovered from the reference strain for Stenotrophomonas (Xanthomonas or Pseudomonas) maltophilia serogroup O7, after mild acid hydrolysis of the lipopolysaccharide, was constructed from D-rhamnose. By means of chemical degradations and NMR studies, the repeating unit of the polymer was shown to be a linear trisaccharide with the structure -->2)-alpha-D-Rhap-(1-->3)-alpha-D-Rhap-(1-->3)-alpha-D-R hap-(1-->. The same repeating unit is present in the common antigen of Pseudomonas aeruginosa and in O antigens from some pathovars of Pseudomonas syringae and a strain of Burkholderia (Pseudomonas) cepacia.

Structure of the O-7 antigen from Acinetobacter baumannii.

The polymeric O-antigen was isolated from the lipopolysaccharide of the reference of the reference strain for Acinetobacter baumannii serogroup O-7. Both the lipopolysaccharide and the isolated polymer reacted with the homologous antiserum. Monosaccharide analyses and NMR spectra showed that the polymer had a hexasaccharide repeating unit constructed from residues of L-rhamnose (4) and N-acetyl-D-glucosamine (2). The following structure for the repeating unit was established by means of detailed interpretation of the NMR spectra, methylation analysis, and chemical degradations. The tetrasaccharide backbone is identical to that for the O-10 antigen of A. baumannii, which has alpha-D-ManpNAc as the lateral substituent in place of the disaccharide present in the O-7 antigen. [formula: see text]

Structural characterisation of a rhamnan and a fucorhamnan, both present in the lipopolysaccharide of Burkholderia vietnamiensis strain LMG 10926.

The polymeric fraction isolated after mild acid hydrolysis of the lipopolysaccharide (LPS) from Burkholderia vietnamiensis strain LMG 10926 contained L-rhamnose (Rha) and D-fucose (Fuc). From NMR studies supported by the results of methylation analysis and Smith degradation, it could be inferred that the material was probably a mixture of two glycans. One component was a linear rhamnan with a trisaccharide repeating unit (1); the other was a branched fucorhamnan with a tetrasaccharide repeating unit (2). The presence of two distinct polymeric fractions in LPS is a common feature for Burkholderia species. [structures: see text]

Structural studies of the O-specific side-chain of lipopolysaccharide from Burkholderia gladioli pv. gladioli strain NCPPB 1891.

A polymeric fraction (the O-antigenic side-chain) has been isolated from the lipopolysaccharide of Burkholderia gladioli pv. gladioli strain NCPPB 1891 after mild acid hydrolysis. The components of the polymer and their molar proportions were L-Rha (1), D-Gal (1), D-Man (1), and O-acetyl (1). By means of chemical degradations and NMR studies, the repeating unit of the polymer was shown to be a linear trisaccharide of the structure shown. [formula: see text]

Structure of the O18 antigen from Acinetobacter baumannii.

The polymeric O antigen was obtained from lipopolysaccharide extracted from isolated, defatted cell walls of the reference strain for Acinetobacter baumannii serogroup O18. Monosaccharide analyses and NMR spectra established that the polymer had a regular structure with a repeating unit based on residues of D-galactose (2), N-acetyl-D-galactosamine (1), and N-acetyl-D-mannosamine (1). Further interpretation of the NMR spectra, combined with the results of methylation analysis and a Smith degradation, showed that the repeating unit had the following structure. beta-D-ManpNAc-(1-->4)-alpha-D-Galp 1 decreases 4 -->3)-beta-D-GalpNAc-(1-->3)-beta-D-Galp-(1-->.

Structure of the O2 antigen of Stenotrophomonas (Xanthomonas or Pseudomonas) maltophilia.

An O antigenic polymer containing L-rhamnose, D-mannose, and L-xylose was isolated from the lipopolysaccharide present in the reference strain for Stenotrophomonas (Xanthomonas or Pseudomonas) maltophilia serogroup O2, by mild acid hydrolysis and gel-permeation chromatography. By means of NMR spectroscopy and chemical degradations, the polysaccharide was found to be based on a branched trisaccharide repeating-unit of the structure shown. [formula: see text].

Structures of polymeric products isolated from the lipopolysaccharides of reference strains for Acinetobacter baumannii O23 and O12.

A polysaccharide containing D-galactose (Gal), 2-acetamido-2-deoxy-D-galactose (GalNAc), 2-acetamido-2-deoxy-D-glucose (GlcNAc), and 3-deoxy-3-(D-3-hydroxybutyramido)-D-quinovose (Qui3NR) was isolated from lipopolysaccharide (LPS) obtained from cells walls of the reference strain for Acinetobacter baumannii O23. By means of NMR studies, methylation analysis, and chemical degradations, the repeating unit of the polymer was identified as a branched pentasaccharide with the structure 1. The same polymer was apparently also present in LPS of the reference strain for serogroup O12, together with a second polymer based on a branched tetrasaccharide with the structure 2. This second polymer has previously been isolated as the O16 antigen of A. baumannii [Haseley, S.R., Diggle, H.J. & Wilkinson, S. G. (1996) Carbohydr. Res. 293, 259-265] and is probably present as a minor component of the LPS of A. baumannii O11 [Haseley, S.R. & Wilkinson, S.G. (1996) Eur. J. Biochem. 237, 266-271]. [Sequence: see text]

Identification of capsular antigens in Serratia marcescens.

Previous studies with 31 strains of Serratia marcescens, including 28 reference O-serotype strains, have indicated that 19 of them have an acidic polysaccharide which copurifies with lipopolysaccharide during phenol-water extraction. Polysaccharide in crude extracts from 18 of the 19 strains was precipitated with Cetavlon (hexadecyltrimethyl ammonium bromide), and capsules were demonstrated around these 18 strains by Indian ink exclusion zones. Capsule-antibody binding by the Quellung reaction suggested that the acidic polysaccharide formed the capsule around the bacterial cells. Anticapsular (anti-K) antibody was detected in reference O antisera which had been prepared against boiled whole cells. Cross-titration and absorption studies revealed 14 different K antigens among these strains.

Lipopolysaccharide from Burkholderia vietnamiensis strain LMG 6999 contains two polymers identical to those present in the reference strain for Burkholderia cepacia serogroup O4.

Lipopolysaccharide was isolated from strain LMG 6999 of Burkholderia vietnamiensis. Degradative and NMR spectroscopic studies established the presence of two polymeric fractions based on the following trisaccharide repeating units: I:-->3)-alpha-D-Galp-(1-->3)-beta-D-Galp-(1-->3)-beta-D-GalpNAc- (1-->; II:-->3)-alpha-D-GalpNAc-(1-->3)-beta-D-GalpNAc-(1-->4)- alpha-L-Rhap-(1-->. The same polymers have previously been found together in lipopolysaccharide from the reference strain for Burkholderia cepacia serogroup O4 and, individually, in those from B. cepacia serogroups C (I) and A (II).

Structural studies of the putative O-specific polysaccharide of Acinetobacter baumannii O24 containing 5,7-diamino-3,5,7,9-tetradeoxy-L-glycero-D-galacto-nonulosonic acid.

A polysaccharide containing D-GlcN, 2-amino-2,6-dideoxy-L-galactose (L-FucN), and 7-acetamido-5-acylamino-3,5,7,9-tetradeoxy-L-glycero-D-galacto-nonulo sonic acid (LegAX), in which the acyl group (X) is either S-3-hydroxybutyryl (50%) or acetyl (50%), was isolated by mild acid hydrolysis treatment, followed by gel-permeation chromatography, of the water-soluble lipopolysaccharide from Acinetobacter baumannii serogroup O24. The polysaccharide, characterised by means of monosaccharide analyses, partial acid hydrolysis, methylation analysis and NMR studies, was shown to have a linear tetrasaccharide repeating unit, as depicted below. Serological tests indicated that the polymer corresponded to the O24 antigen. -->6)-alpha-D-GlcpNAc-(1-->3)-alpha-L-FucpNAc-(1-->3)-alpha-D-Glcp NAc-(1-->4)-beta-LegpAX-(1-->.

Structure of the O-specific polysaccharide from Burkholderia vietnamiensis strain LMG 6998.

The putative O-specific polymer containing D-mannose and L-rhamnose was isolated from the lipopolysaccharide obtained from cells walls of Burkholderia vietnamiensis strain LMG 6998. NMR and degradative studies showed that the polymer has a linear trisaccharide repeating-unit of the structure shown. The same polymer carrying an O-acetyl group at position 3 of the 4-substituted mannose residue has previously been found as the O antigen in the related species Burkholderia cepacia serogroup J. [formula: see text]

Structure of the O20 antigen of Stenotrophomonas (Xanthomonas or Pseudomonas) maltophilia.

The O-antigen polymer recovered from the reference strain for Stenotrophomonas (Xanthomonas or Pseudomonas) maltophilia serogroup O20, by mild acid hydrolysis of the lipopolysaccharide, was found to contain D-rhamnose and D-mannose. By means of chemical degradations and NMR studies, the repeating-unit of the polymer was deduced to be a linear tetrasaccharide with the structure shown. -->2)-alpha-D-Manp-(1-->3)-beta-D-Rhap-(1-->2)-alpha-D-Rh ap-(1-->2)-alpha-D- Rhap-(1-->.

Structure of the O-specific polysaccharide of Acinetobacter baumannii O5 containing 2-acetamido-2-deoxy-D-galacturonic acid.

A polysaccharide containing 2-acetamido-2-deoxy-D-glucose (GlcNAc), 2-acetamido-2-deoxy-L-fucose (FucNAc), and 2-acetamido-2-deoxy-D-galacturonic acid (GalNAcA) was isolated from an aqueous phenol extract of lipid-free, isolated cell walls of the reference strain for Acinetobacter baumannii serogroup O5, by mild acid hydrolysis of the extract and chromatography of the water-soluble products on Sephadex G-50. By means of NMR studies, methylation analysis, carboxyl reduction and chemical degradations, the repeating unit of the polymer was identified as a branched tetrasaccharide of the structure shown. The serologically active polymer is believed to correspond to the side chain of the O5 lipopolysaccharide: [table: see text]