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Allelic diversity and population structure in Vibrio cholerae O139 Bengal based on nucleotide sequence analysis.

ABSTRACT: Comparative analysis of gene fragments of six housekeeping loci, distributed around the two chromosomes of Vibrio cholerae, has been carried out for a collection of 29 V. cholerae O139 Bengal strains isolated from India during the first epidemic period (1992 to 1993). A toxigenic O1 ElTor strain from the seventh pandemic and an environmental non-O1/non-O139 strain were also included in this study. All loci studied were polymorphic, with a small number of polymorphic sites in the sequenced fragments. The genetic diversity determined for our O139 population is concordant with a previous multilocus enzyme electrophoresis study in which we analyzed the same V. cholerae O139 strains. In both studies we have found a higher genetic diversity than reported previously in other molecular studies. The results of the present work showed that O139 strains clustered in several lineages of the dendrogram generated from the matrix of allelic mismatches between the different genotypes, a finding which does not support the hypothesis previously reported that the O139 serogroup is a unique clone. The statistical analysis performed in the V. cholerae O139 isolates suggested a clonal population structure. Moreover, the application of the Sawyer's test and split decomposition to detect intragenic recombination in the sequenced gene fragments did not indicate the existence of recombination in our O139 population.

SUBMITTER: Farfan M

PROVIDER: S-EPMC134837 | biostudies-literature | 2002 Mar

REPOSITORIES: biostudies-literature

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Allelic diversity and population structure in Vibrio cholerae O139 Bengal based on nucleotide sequence analysis.

Farfán M M Miñana-Galbis D D Fusté M C MC Lorén J G JG

Journal of bacteriology 20020301 5

Comparative analysis of gene fragments of six housekeeping loci, distributed around the two chromosomes of Vibrio cholerae, has been carried out for a collection of 29 V. cholerae O139 Bengal strains isolated from India during the first epidemic period (1992 to 1993). A toxigenic O1 ElTor strain from the seventh pandemic and an environmental non-O1/non-O139 strain were also included in this study. All loci studied were polymorphic, with a small number of polymorphic sites in the sequenced fragme ...[more]

PMID: 11844759

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Project description:BACKGROUND: Vibrio cholerae O139 Bengal is the only serogroup other than O1 implicated in cholera epidemics. We describe the isolation and characterization of an O139 serogroup-specific phage, vB_VchP_VchO139-I (?VchO139-I) that has similar host range and virion morphology as phage vB_VchP_JA1 (?JA1) described previously. We aimed at a complete molecular characterization of both phages and elucidation of their genetic and structural differences and assessment of their genetic relatedness to the N4-like phage group. METHODS: Host-range analysis and plaque morphology screening were done for both ?JA1 and ?VchO139-I. Both phage genomes were sequenced by a 454 and Sanger hybrid approach. Genomes were annotated and protein homologies were determined by Blast and HHPred. Restriction profiles, PFGE patterns and data on the physical genome structure were acquired and phylogenetic analyses were performed. RESULTS: The host specificity of ?JA1 has been attributed to the unique capsular O-antigen produced by O139 strains. Plaque morphologies of the two phages were different; ?VchO139-I produced a larger halo around the plaques than ?JA1. Restriction profiles of ?JA1 and ?VchO139-I genomes were also different. The genomes of ?JA1 and ?VchO139-I consisted of linear double-stranded DNA of 71,252 and 70,938 base pairs. The presence of direct terminal repeats of around 1974 base pairs was demonstrated. Whole genome comparison revealed single nucleotide polymorphisms, small insertions/deletions and differences in gene content. Both genomes had 79 predicted protein encoding sequences, of which only 59 were identical between the two closely related phages. They also encoded one tRNA-Arg gene, an intein within the large terminase gene, and four homing endonuclease genes. Whole genome phylogenetic analyses of ?JA1 and ?VchO139-I against other sequenced N4-like phages delineate three novel subgroups or clades within this phage family. CONCLUSIONS: The closely related phages feature significant genetic differences, in spite of being morphologically identical. The phage morphology, genetic organization, genomic content and large terminase protein based phylogeny support the placement of these two phages in the Podoviridae family, more specifically within the N4-like phage group. The physical genome structure of ?JA1 could be demonstrated experimentally. Our data pave the way for potential use of ?JA1 and ?VchO139-I in Vibrio cholerae typing and control.

Dataset Information

Allelic diversity and population structure in Vibrio cholerae O139 Bengal based on nucleotide sequence analysis.

Publications

Allelic diversity and population structure in Vibrio cholerae O139 Bengal based on nucleotide sequence analysis.

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