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Applied and Environmental Microbiology, March 2000, p. 1133-1138, Vol. 66, No. 3
Tsuruga Institute of Biotechnology, Toyobo
Co., Ltd., Tsuruga, Fukui 914-0047, Japan
Received 13 August 1999/Accepted 6 December 1999
IS1203v is an insertion sequence which has been found
in inactivated Shiga toxin 2 genes of Escherichia coli
O157:H7. We analyzed the transpositional mechanism of
IS1203v in order to investigate whether the Shiga toxin 2 genes inactivated by IS1203v could revert to the wild type.
When the transposase activity of IS1203v was enhanced by
artificial frameshifting, IS1203v was obviously excised from the Shiga toxin 2 gene in a circular form. The IS1203v
circle consisted of the entire IS1203v, but an extra 3-bp
sequence (ATC) intervened between the 5' and 3' ends of
IS1203v. The extra 3-bp sequence was identical to a direct
repeat which was probably generated upon insertion. Moreover, we
detected the Shiga toxin 2 gene with a precise excision of
IS1203v. In the wild-type situation, the transposition
products of IS1203v could be observed by PCR amplification. These results show that IS1203v can transpose in a
nonreplicative manner and that the Shiga toxin gene inactivated by this
insertion sequence can revert to the wild type.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Reactivation of Insertionally Inactivated Shiga
Toxin 2 Genes of Escherichia coli O157:H7 Caused by
Nonreplicative Transposition of the Insertion Sequence
*
Corresponding author. Mailing address: Tsuruga
Institute of Biotechnology, Toyobo Co., Ltd., 10-24 Toyo-cho, Tsuruga,
Fukui 914-0047, Japan. Phone: 81-770-22-7643. Fax: 81-770-22-7671. E-mail: masahiro_kusumoto{at}bio.toyobo.co.jp.
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