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

肠出血性大肠杆菌O157在人类中引起严重的食源性疾病。肠出血性大肠杆菌的关键毒力因子是志贺毒素（Stx1和Stx2），这两种毒素是由羔羊样噬菌体编码的。已知Stx1和Stx2的可产性在菌株之间存在差异，但原因尚不清楚。在本研究中，为了揭示O157菌株毒素生产多样性的基因组背景，我们对Stx噬菌体进行了精细的比较。日本O157株中Stx1和Stx2的产生水平存在较大差异。我们没有发现毒素产率与菌株系群之间的相关性。通过比较基因组学，我们发现Stx噬菌体基因组具有高度的基因组多样性。现在，我们正在分析毒素产量与Stx噬菌体类型之间的关系。

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.