Article

O-antigen variation in Salmonella spp.: Rfb gene clusters of three strains

Department of Microbiology, University of Sydney, New South Wales, Australia.
Journal of Bacteriology (Impact Factor: 2.69). 02/1988; 170(1):103-7.
Source: PubMed

ABSTRACT The O antigens of Salmonella serogroups A, B, and D differ structurally in their side-chain sugar residue. These genes encoding O-antigen biosynthesis are clustered in the rfb operon. We report here the molecular cloning and analysis of the rfb operons of Salmonella paratyphi A (serogroup A) and S. typhi (serogroup D). The regions of DNA nonhomology between the rfb operons of these serogroup A, B, and D representatives are identified, and the evolutionary derivation of serogroup A from a serogroup D progenitor is discussed.

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Available from: Neil Quigley, Aug 18, 2015
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    • "The basic structures of the repeating units of serogroups A, B, and D are comprised of four sugars, three of which form a backbone (mannosyl–rhamnosyl–galactose). The fourth side chain sugar is the only variation among the three serogroups: abequose for serogroup B, tyvelose for serogroup D, and paratose for serogroup A (Verma et al., 1988). The rfbJ, rfbS, and rfbE genes are associated with the phenotypic differences of these serogroups (Liu, et al., 1991). "
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    ABSTRACT: Comparative genomic approaches provide abundant information to reveal the diversity among Salmonella serogroups. In a local genomic sequence database, twenty-five Salmonella whole genomic sequences were divided into 6 (A, B, C1, C2, D and others) serogroups for mining the DNA fragments specific for serogroups A through D. For each serogroup, a reference sequence was selected and split into 1000-bp fragments in silico to align against all the other genomic sequences to obtain one or more serogroup-specific fragments. As a result, 2, 6, 7, 10, and 7 specific fragments were found for A, B, C1, C2 and D serogroups, respectively. Specific primer sets targeting these DNA fragments were designed for multiplex PCR assays identifying 21 Salmonella standard strains and 86 additional food isolates. The PCR results demonstrated good agreement with those from Salmonella serotyping. This means that the PCR assay may be able to identify 5 (A, B, C1, C2 and D) Salmonella serogroups and elucidate differences among them. Based on the gene annotations, the 32 serogroup-specific fragments were divided into 3 categories (membrane protein genes, rfb gene clusters, and fimbrial genes). Each gene from these three groups was conserved within the serogroup and was closely correlated with phenotypic characterization. This finding implies that these genes, which are associated with sugar synthesis and metabolism or glycosyl and O-actetyl transfer, impart the differences among Salmonella serogroups.
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