Role of genomic rearrangements in producing new ribotypes of Salmonella typhi.
Salmonella typhi is the only species of Salmonella which grows exclusively in humans, in whom it causes enteric typhoid fever. Strains of S. typhi show very little variation in electrophoretic types, restriction fragment length polymorphisms, cell envelope proteins, and intervening sequences, but the same strains are very heterogeneous for ribotypes which are detected with the restriction endonuclease PstI. In addition, the genome of S. typhi has been proven to undergo genomic rearrangement due to homologous recombination between the seven copies of rrn genes. The relationship between ribotype heterogeneity and genomic rearrangement was investigated. Strains of S. typhi which belong to 23 different genome types were analyzed by ribotyping. A limited number of ribotypes were found within the same genome type group; e. g., most strains of genome type 3 belonged to only two different ribotypes, which result from recombination between rrnH and rrnG operons. Different genome type groups normally have different ribotypes. The size and identity of the PstI fragment containing each of the seven different rrn operons from S. typhi Ty2 were determined, and from these data, one can infer how genomic rearrangement forms new ribotypes. It is postulated that genomic rearrangement, rather than mutation, is largely responsible for producing the ribotype heterogeneity in S. typhi.
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Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
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Sanderson
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D015373:Bacterial Typing Techniques; D015139:Blotting, Southern; D015342:DNA Probes; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D016521:Electrophoresis, Gel, Pulsed-Field; D005798:Genes, Bacterial / Q000235:genetics; D020459:Genes, rRNA / Q000235:genetics*; D016680:Genome, Bacterial; D005838:Genotype; D011995:Recombination, Genetic; D012485:Salmonella typhi / Q000145:classification* / Q000235:genetics*; D012407:rRNA Operon
D015342:DNA Probes; C024388:CTGCAG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific