Małgorzata Mieszała

The occurrence of glycine in bacterial lipopolysaccharides

The aminoacyl analysis of endotoxic lipopolysaccharides (LPS) isolated from several bacteria revealed essential amounts of glycine, among the inherent LPS components. Significant amounts of the glycine was detected in lipopolysaccharides isolated from over 30 strains of Escherichia, Salmonella, Hafnia, Citrobacter and Shigella species. Glycine as a single amino acid was found only in a core part of LPS. Molar ratio of glycine in core oligosaccharide fraction ranged from 0.2 to 0.6 per 3 heptoses. The oligosaccharide enriched in glycine was isolated using the HPLC. The amino acid appeared to be terminally located in a core oligosaccharide. The labelling of the lipopolysaccharide cores was achieved when the bacteria were cultivated in the presence of radioactive [14C]glycine. The labelled core oligosaccharide released the radioactivity during treatment with mild alkali or acid (0.1 M NaOH or HCl, 100 degrees C, 4 h). The radioactivity in SDS-polyacrylamide gel electrophoresis migrated exclusively with LPS. The results indicate that amino acid is an integral constituent of core oligosaccharide in lipopolysaccharide.

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.

Structural heterogeneity of the sialic-acid-containing oligosaccharides from the lipopolysaccharide of Hafnia alvei strain 2 as detected by FABMS studies☆

The structure of four oligosaccharide fractions from the Hafnia alvei strain 2 lipopolysaccharide (LPS) have been assigned by FABMS. This approach corroborates data previously established by NMR spectroscopy for the major oligosaccharides in these fractions [A. Gamian, E. Romanowska, U. Dabrowski, J. Dabrowski, Biochemistry 30 (1991) 5032-5038; E. Katzenellenbogen, A. Gamian, E. Romanowska, U. Dabrowski, J. Dabrowski, Biochem. Biophys. Res. Commun. 194 (1993) 1058-1064; N. Ravenscroft, A. Gamian, E. Romanowska, Eur. J. Biochem. 227 (1995) 889-896]. In addition, the MS/MS with B/E linked scan technique allowed the detection of an additional oligosaccharide with the structure: [formula: see text] lacking the branched O-6 linked glucopyranose residue at the 3-linked Gal unit, which indicates a structural heterogeneity for the major oligosaccharide fraction.

Re-classification within the serogroups O3 and O8 of Citrobacter strains

BackgroundCitrobacter strains are opportunistic pathogens often responsible for serious enteric as well as extra-intestinal diseases, and therefore the O-antigenic scheme, still in use in diagnostic identification, should be set for proper serotyping. The structures of more than 30 different Citrobacter O-antigens (O-polysaccharide chains of the lipopolysaccharides) of 43 Citrobacter O-serogroups have been elucidated so far. However, relationships between strains in several heterogeneous serogroups still need to be clarified by immunochemical studies. These include complex serogroups O3 and O8, represented by 20 and 7 strains, respectively, which are the subject of the present work. Earlier, the O-polysaccharide structures have been determined for Citrobacter O3 strain Be35/57 (PCM 1508) and Citrobacter O8 strain Be64/57 (PCM 1536).ResultsSerological studies (immunoblotting) carried out on Citrobacter lipopolysaccharides from different strains ascribed to serogroups O3 and O8 showed that each of these serogroups should be divided into non-cross-reacting subgroups. Based on the results of chemical analyses and 1H and 13C NMR spectroscopy the structure of Citrobacter O-antigens from strains PCM 1504 (O6) and PCM 1573 (O2) have been established. Chemical data combined with serological analyses showed that several Citrobacter strains should be reclassified into other serogroups.ConclusionsImmunochemical studies carried out on Citrobacter LPS, described in this paper, showed the expediency of reclassification of: 1) strains PCM 1504 and PCM 1573 from serogroups O6 and O2 to serogroups O3 and O8, respectively, 2) strains PCM 1503 and PCM 1505 from serogroups O3 and O8 to new serogroups O3a and O8a, respectively.

O-Aminoacylation of Bacterial Glycoconjugates: From Native Structure to Vaccine Design

The aminoacylation of bacterial polysaccharide antigens and its biological role are poorly understood, although it might be relevant in infection and immunity. Due to the lability of ester-linked substituents on glycoconjugate antigens, such groups usually escape detection during routine structural investigation. Of the few data available, those on the occurrence of glycine in the endotoxic lipopolysaccharides of Gram-negative bacteria are well documented. This article summarizes these data on glycine as an integral constituent of bacterial LPS and also some other amino-acid esters in the teichoic acids and phosphatidylglycerol of Gram-positive bacteria. The possible functions of such noncarbohydrate ester-linked substituents in bacterial antigens are discussed. Because glycine, an inherent component of bacterial lipopolysaccharides in the core region, is supposed to participate in epitope formation, such a structure may be considered for potential use in the construction of a vaccine with broad specificity.

S19.7 Studies on glycine as a component of bacterial lipopolysaccharides

The aminoacyl analysis of endotoxic lipopolysaccharides (LPS) isolated from several bacteria revealed the essential amounts of glycine, among the inherent LPS components. This prompts for the detailed investigation in view of the search for common epitopes suitable for construction of antimicrobial vaccine with broad specificity. The glycine, possibly unifying the LPS structures, might create the common epitope. Significant amounts of glycine was detected in lipopolysaccharides isolated from over 30 strains of Shigella, Escherichia coli, Salmonella, Hafnia and Citrobacter. When the O-specific polysaccharide, lipid A and core fractions of Shigella flexneri and sonnei LPSs were subjected to aminoacyl analysis, glycine as a single aminoacid was found only in core oligosaccharide. The quantity of the aminoacid was not stoichiometric in core oligosaccharides. Molar ratio of glycine ranged from 0.2 to 0.6 per 3 heptoses. Using the HPLC the oligosaccharide enriched in glycine was isolated. Mild acid treatment (0.05 M HC1, 15 min, 100°C) released free glycine. The aminoacid could be also partially cleaved (in 50°70) by pronase digestion. Growing E. coli C600 or Sh. sonnei phase II in the presence of radioactive ~4C-Gly, the labelling of their lipopolysaccharide cores was achieved. The experiments indicate that glycine is covalently bound component of core oligosaccharide in bacterial lipopolysaccharides.