title: Deletion of the Shiga toxin gene in a chlorate-resistant derivative of Shigella dysenteriae type 1 that retains virulence.
abstract: We used a probe specific for detecting the structural-gene sequences of Shiga toxin to analyze the genetic nature of toxin synthesis in mutant derivatives of Shigella dysenteriae type 1. A chlorate-resistant (chl) mutant (725-78) of S. dysenteriae type 1 strain 3818T, which had retained virulence but had lost production of high levels of cytotoxic activity associated with Shiga toxin synthesis, contained a complete deletion of the Shiga toxin structural-gene sequences. These structural-gene sequences were also absent in a derivative of S. dysenteriae type 1 that contained a substitution of Escherichia coli DNA in the trp region of the chromosome. Isolates of Shigella flexneri and Shigella sonnei also did not react with the probe. The low-level cytotoxic activities associated with the mutant S. dysenteriae type 1 strains or with the virulent S. flexneri and S. sonnei strains are neutralizable with antiserum to Shiga toxin; however, these cytotoxic activities are not determined by the genes encoding classic Shiga toxin.
mesh_terms: D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics*; D015139:Blotting, Southern; D002704:Chlorates / Q000494:pharmacology; D002872:Chromosome Deletion; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D004352:Drug Resistance, Microbial; D005798:Genes, Bacterial; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D009693:Nucleic Acid Hybridization; D022603:Shiga Toxins; D012762:Shigella dysenteriae / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D014774:Virulence
chemical_list: D001427:Bacterial Toxins; D002704:Chlorates; D004269:DNA, Bacterial; D022603:Shiga Toxins