Identification of genomic region that confers Stx2 producibility of Stx2phages in Escherichia coli O157.

肠出血性大肠杆菌（EHEC）O157可导致人类严重的食源性疾病。肠出血性大肠杆菌的关键毒力因子是由类噬菌体编码的滋贺毒素（Stx 1和Stx 2）。已知Stx 1和Stx 2的产生在菌株之间是多样化的，但原因仍然不清楚。为了揭示O157菌株产毒多样性的基因组背景，我们对Stx菌株进行了精细的比较。在日本分离的O157菌株中，Stx1和Stx2的产生水平差异很大。未发现菌株产毒量与菌株群间的相关性。通过比较基因组学研究，我们发现Stx噬菌体基因组之间存在高度的基因组多样性。目前，我们正在分析毒素产生与Stx噬菌体类型的相关性。

Enterohemorrhagic Escherichia coli (EHEC) O157 causes severe food-borne illness in humans. The key virulence factor of EHEC is Shiga toxins (Stx1 and Stx2), which are encoded by lambdoid bacteriophages. It is known that producibility of both Stx1 and Stx2 are diversified among strains, but the reasons remain obscure. In this study, in order to reveal the genomic context of the diversity of toxin producibility among O157 strains, we performed fine comparison of Stx phages. Stx1 and Stx2 production levels among O157 strains isolated in Japan were highly divergent. We could not found any correlation between toxin producibility and phylogroups of strains. By comparative genomics, we found high degree of genomic diversity among Stx phage genomes. Now, we are analyzing correlation between toxin producibility and Stx phage types.