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.
- SourceAvailable from: Dominique Galli[Show abstract] [Hide abstract]
ABSTRACT: Distribution of plasmid molecules to the two daughter cells at cell division is of major importance for their stable inheritance. Several mechanisms that control equipartitioning of low-copy-number plasmids have been described in molecular terms. However, no homologous or analogous systems have been identified for intermediate or high-copy-number plasmids, including rolling circle replicating (RCR) plasmids. It has been suggested that distribution of such plasmids at cell division relies solely on random segregation. Plasmid pVT736-1 is a 2 kb RCR plasmid that was isolated from the Gram-negative capnophilic coccobacillus Actinobacillus actinomycetemcomitans. The plasmid contains a DNA region of approximately 0.8 kb that is associated with its segregational stability. An operon that consists of two genes (orf3 and orf2) is followed by a putative cis-acting site that contains an integration host factor (IHF) binding site, flanked by several repeats. Mutations in orf2 resulted in plasmid instability. In addition, this DNA region was able to stabilize partially a heterologous replicon, p15A. Homologues or analogues of the pVT736-1 stabilization system have been detected on numerous plasmid and bacterial genomes.Molecular Microbiology 08/1997; 25(04):649-659. · 5.03 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Dichelobacter nodosus, the etiological agent of ovine footrot, exists both as virulent and as benign strains, which differ in virulence mainly due to subtle differences in the three subtilisin-like proteases AprV2, AprV5 and BprV found in virulent, and AprB2, AprB5 and BprB in benign strains of D. nodosus. Our objective was a molecular genetic epidemiological analysis of the genes of these proteases by direct sequence analysis from clinical material of sheep from herds with and without history of footrot from 4 different European countries. The data reveal the two proteases known as virulent AprV2 and benign AprB2 to correlate fully to the clinical status of the individuals or the footrot history of the herd. In samples taken from affected herds, the aprV2 gene was found as a single allele whereas in samples from unaffected herds several alleles with minor modifications of the aprB2 gene were detected. The different alleles of aprB2 were related to the herds. The aprV5 and aprB5 genes were found in the form of several alleles scattered without distinction between affected and non-affected herds. However, all different alleles of aprV5 and aprB5 encode the same amino acid sequences, indicating the existence of a single protease isoenzyme 5 in both benign and virulent strains. The genes of the basic proteases BprV and BprB also exist as various alleles. However, differences found in samples from affected versus non-affected herds do not reflect the currently known epitopes that are attributed to differences in biochemical activity. The data of the study confirm the prominent role of AprV2 in the virulence of D. nodosus and shed a new light on the presence of the other protease genes and their allelic variants in clinical samples.Veterinary Microbiology 11/2013; · 3.13 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Tst, the gene for toxic shock syndrome toxin-1 (TSST-1), is part of a 15.2 kb genetic element in Staphylococcus aureus that is absent in TSST-1-negative strains. The prototype, in RN4282, is flanked by a 17 nucleotide direct repeat and contains genes for a second possible superantigen toxin, a Dichelobacter nodosus VapE homologue and a putative integrase. It is readily transferred to a recA− recipient, and it always inserts into a unique chromosomal copy of the 17 nucleotide sequence in the same orientation. It is excised and circularized by staphylococcal phages φ13 and 80α and replicates during the growth of the latter, which transduces it at very high frequency. Because of its site and orientation specificity and because it lacks other identifiable phage-like genes, we consider it to be a pathogenicity island (PI) rather than a transposon or a defective phage. The tst element in RN4282, near tyrB, is designated SaPI1. That in RN3984 in the trp region is only partially homologous to SaPI1 and is excised by phage 80 but not by 80α. It is designated SaPI2. These PIs are the first in any Gram-positive species and the first for which mobility has been demonstrated. Their mobility may be responsible for the spread of TSST-1 production among S. aureus strains.Molecular Microbiology 04/2002; 29(2):527 - 543. · 5.03 Impact Factor