Sequence of a variant Shiga-like toxin type-I operon of Escherichia coli O111:H-.
PCR amplification was used to screen faecal isolates of Escherichia coli from a 12-month-old boy with haemolytic uraemic syndrome for the presence of Shiga-like toxin (SLT)-encoding genes. One isolate, belonging to serotype O111:H-, was positive for SLT-I by this method. UV induction indicated that the strain was lysogenic for a lambdoid bacteriophage, but this did not encode the toxin. Southern hybridization analysis of chromosomal DNA revealed that the SLT-I gene was located on an 8.5-kb EcoRI fragment. SLT-I was further localized to within a 3.0-kb SphI-EcoRI fragment. A separate subclone contained a 3.75-kb HindIII fragment, 1.18 kb of which was common to both. Nucleotide sequence analysis of derivatives of these clones revealed that the SLT-I A subunit gene from E. coli O111:H- differed from the previously published sequences for SLT-I by 5 bp [resulting in two amino acid (aa) changes]. It was more closely related to the gene encoding the A subunit of the Shiga toxin from Shigella dysenteriae type 1, from which it differed by 3 bp (resulting in one aa change). The DNA sequence of the B subunit-encoding gene was identical to that of the other two toxins. The region of DNA upstream from the SLT-I of E. coli O111:H- contained an IS element, as well as a region with strong homology to a portion of the genome of bacteriophage lambda.
Paton
A W
AW
Department of Microbiology, Adelaide Children's Hospital, Australia.
Paton
J C
JC
Goldwater
P N
PN
Heuzenroeder
M W
MW
Manning
P A
PA
D000595:Amino Acid Sequence; D001427:Bacterial Toxins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D006463:Hemolytic-Uremic Syndrome / Q000382:microbiology; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009876:Operon; D015183:Restriction Mapping; D022622:Shiga Toxin 1
D001427:Bacterial Toxins; D022622:Shiga Toxin 1