Analysis of sequences flanking the vap regions of Dichelobacter nodosus: evidence for multiple integration events, a killer system, and a new genetic element.
Dichelobacter nodosus is the causative agent of ovine footrot. The vap regions of the D. nodosus genome may have arisen by the integration of a genetic element and may have a role in virulence. The virulent D. nodosus strain A198 has multiple copies of the vap regions. In the present study, sequences to the left and right of vap regions 1, 2 and 3 of strain A198 were analysed by Southern blotting and DNa sequencing. The results suggest that vap regions 1 and 2 rose by independent integration events into different tRNA genes. The discovery of a second integrase gene (intB), a gene with similarity to bacteriophage repressor proteins (regA), and a gene similar to an ORF from a conjugative transposon (gepA), suggests that a second genetic element, either a bacteriophage or a conjugative transposon, is integrated next to vap region 3 in the D. nodosus genome. The arrangement of intB and the vap regions in three other virulent strains and one benign strain was determined using using Southern blotting and PCR. One strain, H1215, contained vapE' and not vapE, and thus resembles vap region 3, suggesting that vap region 3 also may have arisen by an independent integration event. In all strains, a copy of intB was found next to the vap regions. The vap regions contain two genes, vapA and toxA, with similarity to the hig genes of the killer plasmid Rts1. Evidence is presented that vapA and toxA have a similar function in D. nodosus.
Bloomfield
Garry A
GA
Department of Molecular and Cellular Biology, The University of New England, Armidale, NSW 2351, Australia.
Whittle
Gabrielle
G
Department of Molecular and Cellular Biology, The University of New England, Armidale, NSW 2351, Australia.
McDonagh
Matthew B
MB
Department of Molecular and Cellular Biology, The University of New England, Armidale, NSW 2351, Australia.
Katz
Margaret E
ME
Department of Molecular and Cellular Biology, The University of New England, Armidale, NSW 2351, Australia.
Cheetham
Brian F
BF
Department of Molecular and Cellular Biology, The University of New England, Armidale, NSW 2351, Australia.
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D001439:Bacteroides / Q000235:genetics* / Q000472:pathogenicity; D001483:Base Sequence; D003227:Conjugation, Genetic; D004251:DNA Transposable Elements / Q000235:genetics*; D005535:Foot Rot / Q000382:microbiology; D018014:Gene Transfer Techniques; D005798:Genes, Bacterial; D019426:Integrases / Q000235:genetics; D008562:Membrane Glycoproteins / Q000235:genetics; D008969:Molecular Sequence Data; D012329:RNA, Bacterial / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics; D011995:Recombination, Genetic; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012756:Sheep; D012757:Sheep Diseases / Q000382:microbiology; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D008562:Membrane Glycoproteins; D012329:RNA, Bacterial; D037521:Virulence Factors; D012343:RNA, Transfer; D019426:Integrases