Genetic structure and chromosomal integration site of the cryptic prophage CP-1639 encoding Shiga toxin 1.
The sequence of 50 625 bp of chromosomal DNA derived from Shiga-toxin (Stx)-producing Escherichia coli (STEC) O111: H- strain 1639/77 was determined. This DNA fragment contains the cryptic Stx1-encoding prophage CP-1639 and its flanking chromosomal regions. The genome of CP-1639 basically resembles that of lambdoid phages in structure, but contains three IS629 elements, one of which disrupts the gene of a tail fibre component. The prophage genome lacks parts of the recombination region including integrase and excisionase genes. Moreover, a capsid protein gene is absent. CP-1639 is closely associated with an integrase gene of an ancient integrative element. This element consists of three ORFs of unknown origin and a truncated integrase gene homologous to intA of CP4-57. By PCR analysis and sequencing, it was shown that this integrative element is present in a number of non-O157 STEC serotypes and in non-STEC strains, where it is located at the 3'-end of the chromosomal ssrA gene. Whereas in most E. coli O111: H- strains, prophages are inserted in this site, E. coli O26 strains contain the integrative element not connected to a prophage. In E. coli O103 strains, the genetic structure of this region is variable. Comparison of DNA sequences of this particular site in E. coli O157: H7 strain EDL933, E. coli O111: H- strain 1639/77 and E. coli K-12 strain MG1655 showed that the ssrA gene is associated in all cases with the presence of foreign DNA. The results of this study have shown that the cryptic prophage CP-1639 is associated with an integrative element at a particular site in the E. coli chromosome that possesses high genetic variability.
Creuzburg
Kristina
K
Institut für Medizinische Mikrobiologie und Hygiene der TU Dresden, Germany.
Köhler
Bernd
B
Institut für Hygiene und Mikrobiologie der Bayerischen Julius Maximilians Universität Würzburg, Germany.
Hempel
Helena
H
Institut für Medizinische Mikrobiologie und Hygiene der TU Dresden, Germany.
Schreier
Peter
P
Lehrstuhl für Lebensmittelchemie der Bayerischen Julius Maximilians Universität Würzburg, Germany.
Jacobs
Enno
E
Institut für Medizinische Mikrobiologie und Hygiene der TU Dresden, Germany.
Schmidt
Herbert
H
Institut für Medizinische Mikrobiologie und Hygiene der TU Dresden, Germany.
D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D039002:Prophages / Q000737:chemistry / Q000235:genetics*; D012329:RNA, Bacterial / Q000235:genetics*; D017422:Sequence Analysis, DNA; D012703:Serotyping; D022622:Shiga Toxin 1 / Q000235:genetics*; D016662:Virus Integration
D012329:RNA, Bacterial; D022622:Shiga Toxin 1; C096222:tmRNA