Hayashi T, Makino K, Ohnishi M, Kurokawa K, Ishii K, Yokoyama K, Han C G, Ohtsubo E, Nakayama K, Murata T, Tanaka M, Tobe T, Iida T, Takami H, Honda T, Sasakawa C, Ogasawara N, Yasunaga T, Kuhara S, Shiba T, Hattori M, Shinagawa H
Department of Microbiology, Miyazaki Medical College, Kiyotake, Japan.
DNA Res. 2001 Feb 28;8(1):11-22. doi: 10.1093/dnares/8.1.11.
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.
大肠杆菌O157:H7是一种主要的食源性感染病原体，可导致腹泻、出血性结肠炎和溶血性尿毒综合征。在此，我们报告从阪井疫情中分离出的一株O157:H7菌株的完整染色体序列，以及与良性实验室菌株K-12 MG1655的基因组比较结果。该染色体大小为5.5 Mb，比K-12的染色体大859 Kb。我们鉴定出两株菌株之间高度保守的4.1-Mb序列，这可能代表了大肠杆菌染色体的基本骨架。其余的1.4-Mb序列由O157:H7特异性序列组成，其中大部分是水平转移的外源DNA。噬菌体在O157:H7出现过程中的主要作用通过24个原噬菌体和原噬菌体样元件的存在得以体现，这些元件占据了O157:H7特异性序列的一半以上。O157:H7染色体编码1632种蛋白质和20种K-12中不存在的tRNA。其中，至少131种蛋白质被认为具有与毒力相关的功能。全基因组密码子使用分析表明，O157:H7特异性tRNA参与了菌株特异性基因的高效表达。这里展示的一套完整的O157:H7特异性基因，为深入了解O157:H7的致病性和生理学提供了新的视角，并将为全面理解O157:H7感染的分子机制开辟道路。
