Identification of a gene encoding a bacteriophage-related integrase in a vap region of the Dichelobacter nodosus genome.
ABSTRACT Dichelobacter nodosus is the principal causative agent of ovine footrot. Nucleotide (nt) sequences from the D. nodosus genome have been isolated and a series of overlapping lambda clones defining vap (virulence-associated protein) regions 1, 2 and 3 have been reported [Katz et al., J. Bacteriol. 176 (1994) 2663-2669]. In the present study, the limits of the virulence-associated (va) DNA around vap regions 1 and 3 were determined by dot-blot hybridization experiments using plasmid subclones to probe genomic DNA from the D. nodosus virulent strain A198 and the benign strain C305. This va region was found to be approx. 11.9 kb in length, and to be interrupted by a short DNA segment which is also found in the benign D. nodosus strain. Sequence analysis of the entire region revealed an ORF, intA, which is very similar to the integrases of bacteriophages phi R73, P4 and Sf6. Bacteriophages phi R73 and P4 integrate into the 3' ends of tRNA genes, with the integrase genes adjacent to the tRNA genes. A similar arrangement was found in the D. nodosus va region. A 19-bp nt sequence was found to be repeated at the ends of the va region, and may represent the bacteriphage attachment site. These findings suggest that D. nodosus may have acquired these DNA sequences by the integration of a bacteriophage, or an integrative plasmid that contains a bacteriophage-related integrase gene. The high similarity of the D. nodosus integrase to integrases from coliphages suggests that these va sequences may be transferred between distantly related bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)
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ABSTRACT: Major parts of the virulence-associated vrl locus known from the gammaproteobacterium Dichelobacter nodosus, the causative agent of ovine footrot, were analyzed in the genome of the sulfate-reducing deltaproteobacterium Desulfococcus multivorans. In the genome of D. multivorans 13 of the 19 vrl genes described for D. nodosus are present and highly conserved with respect to gene sequence and order. The vrl locus and its flanking regions suggest a bacteriophage-mediated transfer into the genome of D. multivorans. Comparative analysis of the deduced Vrl proteins reveals a wide distribution of parts of the virulence-associated vrl locus in distantly related bacteria. Horizontal transfer is suggested as driving mechanism for the circulation of the vrl genes in bacteria. Except for the vrlBMN genes D. multivorans and Desulfovibrio desulfuricans G20 together contain all vrl genes displaying a high degree of similarity. For D. multivorans it could be shown that guanine plus cytosine (GC) content, GC skew, di-, tri- or tetranucleotide distribution did not differ between the vrl locus and its flanking sequences. This could be a hint that the vrl locus originated from a related organism or at least a genome with similar characteristics. The conspicuous high degree of conservation of the analyzed vrl genes may result from a recent transfer event or reflect a function of the vrl genes, which is still unknown and not necessarily disease associated. The latter is supported by the evidence for expression of the vrl genes in D. multivorans, which has not been described as pathogen or to be associated to any disease pattern before.Journal of Molecular Microbiology and Biotechnology 02/2007; 13(1-3):156-64. · 1.68 Impact Factor
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ABSTRACT: Footrot is a contagious, debilitating disease of sheep, causing major economic losses in most sheep-producing countries. The causative agent is the Gram-negative anaerobe Dichelobacter nodosus. Depending on the virulence of the infective bacterial strain, clinical signs vary from a mild interdigital dermatitis (benign footrot) to severe underrunning of the horn of the hoof (virulent footrot). The aim of this study was to investigate the genetic relationship between D. nodosus strains of different phenotypic virulences and between isolates from different geographic regions. Genome sequencing was performed on 103 D. nodosus isolates from eight different countries. Comparison of these genome sequences revealed that they were highly conserved, with >95% sequence identity. However, single nucleotide polymorphism analysis of the 31,627 nucleotides that were found to differ in one or more of the 103 sequenced isolates divided them into two distinct clades. Remarkably, this division correlated with known virulent and benign phenotypes, as well as with the single amino acid difference between the AprV2 and AprB2 proteases, which are produced by virulent and benign strains, respectively. This division was irrespective of the geographic origin of the isolates. However, within one of these clades, isolates from different geographic regions generally belonged to separate clusters. In summary, we have shown that D. nodosus has a bimodal population structure that is globally conserved and provide evidence that virulent and benign isolates represent two distinct forms of D. nodosus strains. These data have the potential to improve the diagnosis and targeted control of this economically significant disease.mBio 01/2014; 5(5). · 6.88 Impact Factor