Dataset Information

Identification of d-Galactan-III As Part of the Lipopolysaccharide of Klebsiella pneumoniae Serotype O1.

ABSTRACT: Klebsiella pneumoniae is a Gram-negative, ubiquitous bacterium capable of causing severe nosocomial infections in individuals with impaired immune system. Emerging multi-drug resistant strains of this species and particularly carbapenem-resistant strains pose an urgent threat to public health. The lipopolysaccharide (LPS) O-antigen is the main surface antigen. It contributes to the virulence of this species and determines the O-serotype of K. pneumoniae isolates. Among the nine main O-serotypes of K. pneumoniae, O1-and O2-type pathogens are causative agents of over 50% of all infections. Serotype O1, the most common O-serotype, expresses complex LPS consisting of d-galactan-I (a polymer built of ? 3)-?-d-Galf-(1 ? 3)-?-d-Galp-(1 ? repeating units) capped by d-galactan-II (built of [ ? 3)-?-d-Galp-(1 ? 3)-?-d-Galp-(1 ?] repeating units). Galactan-I is present as the sole polymer in O2 serotype. Recently, in case of serotype O2, conversion of galactan-I to galactan-III (? 3)-?-d-Galf-(1 ? 3)-[?-d-Galp-(1 ? 4)]-?-d-Galp-(1 ?) was reported. Substitution of ? 3)-?-d-Galp by a branching terminal ?-d-Galp was dependent on the presence of the gmlABC operon and had a major impact on the antigenicity of the galactan polymer. Genetic analysis indicated that 40% of the O1 clinical isolates also carry the gmlABC locus; therefore we aimed to characterize the corresponding phenotype of LPS O-antigens. The presence of galactan-III among O1 strains was proven using galactan-III-specific monoclonal antibodies and confirmed by structural analyses performed using sugar and methylation analysis as well as classical and high-resolution magic angle spinning NMR spectroscopy. By using an isogenic mutant pair, we demonstrated that galactan-III expression was dependent on the presence of glycosyltransferases encoded by gmlABC, as was shown previously for the O2 serotype. Furthermore, the galactan-II structures in O1gml+ strains remained unaffected corroborating no functional interactions between the biosynthesis of galactan-III and galactan-II polymers.

SUBMITTER: Stojkovic K

PROVIDER: S-EPMC5403891 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Identification of d-Galactan-III As Part of the Lipopolysaccharide of Klebsiella pneumoniae Serotype O1.

Stojkovic Katarina K Szijártó Valéria V Kaszowska Marta M Niedziela Tomasz T Hartl Katharina K Nagy Gábor G Lukasiewicz Jolanta J

Frontiers in microbiology 20170425

Klebsiella pneumoniae is a Gram-negative, ubiquitous bacterium capable of causing severe nosocomial infections in individuals with impaired immune system. Emerging multi-drug resistant strains of this species and particularly carbapenem-resistant strains pose an urgent threat to public health. The lipopolysaccharide (LPS) O-antigen is the main surface antigen. It contributes to the virulence of this species and determines the O-serotype of K. pneumoniae isolates. Among the nine mai ...[more]

PMID: 28487676

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Project description:The lipopolysaccharide O antigens of Klebsiella pneumoniae serotype O1 and Serratia marcescens serotype O16 both contain a repeating unit disaccharide of [-->3)-beta-D-Galf-(1-->3)-alpha-D-Galp-(1-->]; the resulting polymer is known as D-galactan I. In K. pneumoniae serotype O1, the genes responsible for the synthesis of D-galactan I are found in the rfb gene cluster (rfbKpO1). We report here the cloning and analysis of the rfb cluster from S. marcescens serotype O16 (rfbSmO16). This is the first rfb gene cluster examined for the genus Serratia. Synthesis of D-galactan I is an rfe-dependent process for both K. pneumoniae serotype O1 and S. marcescens serotype O16. Hybridization experiments with probes derived from each of the six rfbKpO1 genes indicate that the cloned rfbSmO16 cluster contains homologous genes arranged in the same order. However, the degree of homology at the nucleotide sequence level was sufficiently low that hybridization was detected only under low-stringency conditions. rfbABSmO16 genes were subcloned and shown to encode an ABC-2 (ATP-binding cassette) transporter which is functionally identical to the one encoded by the corresponding rfb genes from K. pneumoniae serotype O1. The amino acid sequences of the predicted RfbA and RfbB homologs showed identities of 75.7% (87.9% total similarity) and 78.0% (86.5% total similarity), respectively. The last gene of the rfbKpO1 cluster, rfbFKpO1, encodes a bifunctional galactosyltransferase which initiates the formation of D-galactan I. RfbFKpO1 and RfbFSmO16 are 57.6% identical (with 71.1% total similarity), and both show similarity with RfpB, the galactosyltransferase involved in the synthesis of Shigella dysenteriae type I O-polysaccharide. The G+C contents of the rfbAB genes from each organism are quite similar, and values are lower than those typical for the species. However, the G+C content of rfbFSmO16 (47.6%) was much higher than that of rfbFKpO1 (37.3%), despite the fact that the average for each species (52 to 60%) falls within the same range.

Dataset Information

Identification of d-Galactan-III As Part of the Lipopolysaccharide of Klebsiella pneumoniae Serotype O1.

Publications

Identification of d-Galactan-III As Part of the Lipopolysaccharide of <i>Klebsiella pneumoniae</i> Serotype O1.

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