Identification of a native Dichelobacter nodosus plasmid and implications for the evolution of the vap regions.
ABSTRACT Studies on the role of various virulence factors of the ovine pathogen, Dichelobacter nodosus, have suffered from the absence of a mechanism for the introduction of DNA into this organism. As an initial step in the development of genetic methods, we have identified and cloned a native 10-kb plasmid, pJIR896, from a clinical isolate. This plasmid was found to be a circular form of vap region 1/3 that is found in the reference strain, A198. However, pJIR896 lacked the duplicated region present in the A198 sequence and instead contained a 1.7-kb putative insertion sequence, IS1253, which shared similarity to a number of unusual IS elements. A model is proposed for the evolution of vap region 1/3 which involves the integration of a plasmid, such as pJIR896, and subsequent rearrangements resulting from the deletion or transposition of IS1253.
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ABSTRACT: Dichelobacter nodosus is the primary pathogen implicated in ovine footrot. In this paper we have delineated a 27 kb locus, termed the virulence-related locus (vrl), that was essentially specific for virulent D. nodosus isolates. The precise ends of this locus were mapped and the sequences of the junction regions from the virulent strain A198 were compared to corresponding sequences from the benign isolate C305. The left end of the vrl locus was located in a sequence similar to that of the small stable 10Sa RNA molecule of Escherichia coli, next to a phage-attachment-site-like sequence, which indicated that the vrl locus might have arisen by the integration of a phage. However, no attachment-like sequence could be found at the right end of the vrl locus. In the chromosome of the benign strain the sequences bordering vrl were not contiguous but were separated by about 3 kb. It was concluded that the divergence of the benign and virulent strains at this locus was a multi-step process. Several potential ORFs were identified at the junction regions but only one ORF, encoding a 126 kDa protein, was expressed in a T7 expression system in E. coli.Microbiology 10/1995; 141 ( Pt 9):2081-9. · 2.85 Impact Factor
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ABSTRACT: The Saccharopolyspora erythraea eryAI and eryAII genes, which, together with eryAIII, are responsible for the formation of the macrolactone portion of the antibiotic erythromycin, are separated by a 1.46-kb segment, designated IS1136, with the characteristics of an insertion sequence. It contains an open reading frame of 425 codons similar to that of the Anabaena IS891 and is present in four nonidentical copies in the Sac. erythraea genome. Inverted repeats were found near the ends of IS1136, and in the copy in eryA, one of the ends was found to overlap the 5' end of eryAII. Hybridization analysis suggests that IS1136 is confined to Saccharopolyspora species containing eryA-homologous DNA.Gene 05/1993; 126(1):147-51. · 2.20 Impact Factor
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ABSTRACT: The virulence properties of various non-typhoid Salmonella serotypes depend on the presence of large plasmids 60-100 kb in size. We have shown previously that the virulence region on the 80 kb plasmid pSDL2 of Salmonella dublin Lane maps within a 14kb SalI fragment. In this report we show that an 8.2 kb region within this fragment is sufficient to express lethal disease in BALB/c mice. Sequence analysis of this segment revealed six sequential open reading frames designated vsdA-F, which encode putative proteins of 13-65kDa. Deletion analysis and location of Tn5-oriT inserts which abolish virulence suggest that vsdA, vsdC, vsdD and vsdE are essential for virulence expression. Downstream of vsdF we discovered a locus involved in stable plasmid maintenance. Deletion of that region resulted in plasmid multimerization and instability.Molecular Microbiology 03/1991; 5(2):307-16. · 4.96 Impact Factor