Journal Article

Chromosome of the Enterohemorrhagic <i>Escherichia coli</i> O157:H7; Comparative Analysis with K-12 MG1655 Revealed the Acquisition of a Large Amount of Foreign DNAs

Makoto Ohnishi, Chiho Tanaka, Satoru Kuhara, Kazuo Ishii, Masahiro Hattori, Ken Kurokawa, Teruo Yasunaga, Kozo Makino, Hideo Shinagawa, Takahiro Murata, Keisuke Nakayama, Yoshiro Terawaki and Tetsuya Hayashi

in DNA Research

Published on behalf of Kazusa DNA Research Institute

Volume 6, issue 6, pages 361-368
Published in print January 1999 | ISSN: 1340-2838
Published online January 1999 | e-ISSN: 1756-1663 | DOI: http://dx.doi.org/10.1093/dnares/6.6.361

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A complete Xba I and Bln I cleavage map was constructed for the chromosome of an enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain isolated from an outbreak in Sakai City, Japan, in 1996. A comparative chromosome analysis with E. coli K-12 strain MG1655 was made. The EHEC chromosome was approximately 5600 kb in length, 1 Mb larger than that of MG1655. Despite the marked difference in chromosome length, the location and direction of seven rRNA operons of the EHEC strain were similar to those for MG1655. Overall organization of genes common in both strains is also highly conserved. Chromosome expansion was observed throughout the EHEC chromosome, albeit in an uneven manner. A large portion of the chromosome enlargement was observed in the region surrounding the replication terminus, particularly in a segment containing the terA locus. Sample sequencing of 3627 random shotgun clones suggested the presence of approximately 1550 kb strain-specific DNAs on the EHEC chromosome, most of which are likely to be of foreign origin.

Keywords: enterohemorrhagic E. coli O157:H7; physical map; chromosome enlargement; horizontal gene transfer; rrn operon

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Subjects: Genetics and Genomics

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