Sequence and structural analysis of the rfb (O antigen) gene cluster from a group C1 Salmonella enterica strain

Lee, Sang Jin; Romana, Lajwant K.; Reeves, Peter R.

doi:10.1099/00221287-138-9-1843

Cited by 64 publications

(46 citation statements)

References 35 publications

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“…Transmembrane region search results indicated that ORF5 had 12 transmembrane segments, while ORF9 contained 9 transmembrane domains. ORF5 is similar to the Ounit flippases of E. coli (62) and Salmonella enterica (23). We deduced that ORF5 might be O-unit flippase and ORF9 might perform the function of polymerization of the O-antigen polysaccharide in PPD134/91.…”

Section: Resultsmentioning

confidence: 92%

NovelAeromonas hydrophilaPPD134/91 Genes Involved in O-Antigen and Capsule Biosynthesis

Zhang¹,

Arakawa

Leung

2002

Infect Immun

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The sequences of the O-antigen and capsule gene clusters of the virulent Aeromonas hydrophila strain PPD134/91 were determined. The O-antigen gene cluster is 17,296 bp long and comprises 17 genes. Seven pathway genes for the synthesis of rhamnose and mannose, six transferase genes, one O unit flippase gene, and one O-antigen chain length determinant gene were identified by amino acid sequence similarity. PCR and Southern blot analysis were performed to survey the distribution of these 17 genes among 11 A. hydrophila strains of different serotypes. A. hydrophila PPD134/91 might belong to serotype O:18, as represented by JCM3980; it contained all the same O-antigen genes as JCM3980 (97 to 100% similarity at the DNA and amino acid levels). The capsule gene cluster of A. hydrophila PPD134/91 is 17,562 bp long and includes 13 genes, which were assembled into three distinct regions similar to those of the group II capsule gene cluster of Escherichia coli and other bacteria. Regions I and III contained four and two capsule transport genes, respectively. Region II had five genes which were highly similar to capsule synthesis pathway genes found in other bacteria. Both the purified O-antigen and capsular polysaccharides increased the ability of the avirulent A. hydrophila strain PPD35/85 to survive in naïve tilapia serum. However, the purified surface polysaccharides had no inhibitory effect on the adhesion of A. hydrophila PPD134/91 to carp epithelial cells.Surface polysaccharides, such as O-antigen and capsule, are important bacterial cell surface components. The O-antigen polysaccharide is covalently ligated to the lipid A-core complex and extends outward from the cell surface. The capsule is an extracellular polysaccharide enclosing the bacterium while remaining attached to the cell. Both the O-antigen polysaccharide and the capsule are composed of repeating oligosaccharide units (44). They act as prominent antigens and play important roles in the pathogenicity of many bacterial pathogens, such as protecting bacterial cells from complement-mediated serum killing (20, 30), acting as adhesion factors (31), protecting the bacteria from the effects of desiccation (38), and aiding survival in phagocytes (56). The serogrouping of bacterial strains within a genus is determined by the structural variability of surface polysaccharides. For example, Escherichia coli strains are divided into more than 160 serogroups based on the different surface polysaccharides (67). Klebsiella species have been classified into 72 serogroups based on the structural variability of their capsular polysaccharides (39).Aeromonas hydrophila is an important pathogen of a wide variety of aquatic and terrestrial animals, especially fish (4). In fish, it causes hemorrhagic septicemia, which often results in high mortalities in commercial aquaculture. Some strains of A. hydrophila are also reported to cause infections in humans. The clinical symptoms include septicemia (17), meningitis (25), peritonitis (35), pneumonia (32), myonecrosis (34), and diarrh...

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Section: Resultsmentioning

confidence: 92%

NovelAeromonas hydrophilaPPD134/91 Genes Involved in O-Antigen and Capsule Biosynthesis

Zhang¹,

Arakawa

Leung

2002

Infect Immun

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“…The rfb regions from serogroups A, B, C2, D, and E, which all have a trisaccharide O subunit containing mannose, rhamnose, and galactose, are related. The rfb gene cluster from serogroup C1, whose O subunit is composed of four mannose residues, one Nacetylglucosamine residue, and a glucose side branch, shows little homology to them [16].…”

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Application of PCR-based serogrouping of selected Salmonella serotypes in Malaysia

Lim

Thong

2009

J Infect Dev Ctries

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Background: Differentiation of Salmonella enterica into its serogroups is important for epidemiological study. The objective of the study was to apply a multiplex PCR targeting serogroups A, B, C1, D, E and Vi-positive strains of Salmonella enterica commonly found in Malaysia. A separate H-typing multiplex PCR which identified flagellar antigen "a", "b" or "d" was also optimized to confirm clinical serotypes, S. Paratyphi A and S. Typhi. Methodology: Sixty-seven laboratory Salmonella enterica strains were tested. Six sets of primers targeting defined regions of the O antigen synthesis genes (rfb gene cluster) and Vi antigen gene (viaB) were selected and combined into a multiplex PCR for O-grouping. Four primers (H-for, Ha-rev, Hb-rev and Hd-rev) were used in the second step multiplex PCR for H-typing. The optimized mPCR assays were further evaluated with 58 blind-coded Salmonella strains. Results: The multiplex PCR results obtained showed 100% concordance to the conventionally typed serogroups. Validation with 58 blind coded Salmonella strains yield 100% accuracy and specificity. Conclusion: Based on this study, PCR serogrouping proved to be a rapid, alternative method for further differentiation of Salmonella enterica.

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“…Sequence analysis revealed unusually low G+C contents for all rib regions investigated, suggesting a relatively recent transfer of the gene cluster to S. enterica from a nonenterobacterial donor with a low G+C content (8,17,22,48).…”

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confidence: 99%

“…A feature common to all rfb gene clusters of S. enterica studied so far is the presence of a gene that encodes a highly hydrophobic polypeptide with 12 predicted membrane-spanning segments (orfl2.8 in strain LT2) (8,17,22,24,48). The function of this protein is unknown; it may assist in the export of the 0 antigen to the cell periphery.…”

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confidence: 99%

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Molecular analysis of the 3,6-dideoxyhexose pathway genes of Yersinia pseudotuberculosis serogroup IIA

1993

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-B, and -C; IVA and -B; and VA and -B), is due to differences in sugar composition and arrangement of the remaining 0 unit (35).In both S. enterica and Y pseudotuberculosis, DDH are formed by the same biosynthetic-reaction sequences. Four DDH, abequose, tyvelose, paratose, and ascarylose, are synthesized by a common pathway proceeding from CDP-D-glucose ( Fig. 1) (28); the fifth, colitose, is derived from GDP-D-mannose presumably via a similar reaction sequence (11). All enzymes involved in DDH biosynthesis in S. enterica are encoded within the rib gene cluster, which is * Corresponding author. responsible for the formation of the O-specific subunit of the LPS (26).The rfb gene clusters of several DDH-containing S. enterica strains have been cloned and sequenced (7,8,17,24,45,50), and most of the DDH-related genes have been identified. In all cases investigated, the arrangement of the DDH pathway genes and their relative positions within the rib region are conserved: immediately downstream of the rhamnose pathway genes, a block of four highly conserved genes is found, comprising rfbF and rfbG as well as two open reading frames (ORFs), orf7.6 and orflO.4, which are thought to correspond to the postulated DDH pathway genes rflI and OJbH (8). Abequose-forming strains of serogroups B and C2 (serovars typhimurium and muenchen, respectively) were shown to possess another gene, rfbJ, coding for abequose synthase, which is located adjacent to this highly conserved block; although secondary structure predictions indicated very similar proteins, DNA and amino acid sequences of the two rfbl genes had only low levels of similarity (only 36% identity at the amino acid level [8]). In strains forming tyvelose and paratose (serovars typhi and paratyphi of serogroups D and A, respectively), the rfbJ gene was replaced by a paratose synthase gene, rUbS, and a tyvelose epimerase gene, rfbE (46). The tyvelose epimerase gene in the paratose-producing group A strain, however, was found to be inactive because of a single point mutation.While rfbS still showed a low degree of similarity to rfib at the DNA sequence level, no counterpart to rfbE was found in the rfb region of the abequose-producing strains of S. enterica. Sequence analysis revealed unusually low G+C contents for all rib regions investigated, suggesting a relatively recent transfer of the gene cluster to S. enterica from a nonenterobacterial donor with a low G+C content (8,17,22,48).We have previously reported the cloning of the Y pseudotuberculosis serogroup IIA rib region (19). Hybridization studies of this abequose-producing strain (M85) had shown that at least some of the M85 rib genes are related to DDH pathway genes (rfbF and rCbG) of S. enterica LT2. In this study, we present the sequence and detailed analysis of the DDH pathway gene region of this Y pseudotuberculosis strain. Most of its DDH pathway genes were clearly related

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Sequence and structural analysis of the rfb (O antigen) gene cluster from a group C1 Salmonella enterica strain

Cited by 64 publications

References 35 publications

NovelAeromonas hydrophilaPPD134/91 Genes Involved in O-Antigen and Capsule Biosynthesis

NovelAeromonas hydrophilaPPD134/91 Genes Involved in O-Antigen and Capsule Biosynthesis

Application of PCR-based serogrouping of selected Salmonella serotypes in Malaysia

Molecular analysis of the 3,6-dideoxyhexose pathway genes of Yersinia pseudotuberculosis serogroup IIA

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