Complete genome sequence of enterohemorrhagic Escherichia coli O157:H7 and genomic comparison with a laboratory strain K-12. |
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Authors: | T Hayashi K Makino M Ohnishi K Kurokawa K Ishii K Yokoyama C G Han E Ohtsubo K Nakayama T Murata M Tanaka T Tobe T Iida H Takami T Honda C Sasakawa N Ogasawara T Yasunaga S Kuhara T Shiba M Hattori H Shinagawa |
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Affiliation: | Department of Microbiology, Miyazaki Medical College, Kiyotake, Japan. thayash@fc.miyazaki-med.ac.jp |
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Abstract: | Escherichia coli O157:H7 is a major food-borne infectious pathogen that causes diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. Here we report the complete chromosome sequence of an O157:H7 strain isolated from the Sakai outbreak, and the results of genomic comparison with a benign laboratory strain, K-12 MG1655. The chromosome is 5.5 Mb in size, 859 Kb larger than that of K-12. We identified a 4.1-Mb sequence highly conserved between the two strains, which may represent the fundamental backbone of the E. coli chromosome. The remaining 1.4-Mb sequence comprises of O157:H7-specific sequences, most of which are horizontally transferred foreign DNAs. The predominant roles of bacteriophages in the emergence of O157:H7 is evident by the presence of 24 prophages and prophage-like elements that occupy more than half of the O157:H7-specific sequences. The O157:H7 chromosome encodes 1632 proteins and 20 tRNAs that are not present in K-12. Among these, at least 131 proteins are assumed to have virulence-related functions. Genome-wide codon usage analysis suggested that the O157:H7-specific tRNAs are involved in the efficient expression of the strain-specific genes. A complete set of the genes specific to O157:H7 presented here sheds new insight into the pathogenicity and the physiology of O157:H7, and will open a way to fully understand the molecular mechanisms underlying the O157:H7 infection. |
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Keywords: | E. coli O157:H7 genome sequence E. coli K-12 bacterial pathogenicity evolution |
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