Yokoyama K, Makino K, Kubota Y, Watanabe M, Kimura S, Yutsudo C H, Kurokawa K, Ishii K, Hattori M, Tatsuno I, Abe H, Yoh M, Iida T, Ohnishi M, Hayashi T, Yasunaga T, Honda T, Sasakawa C, Shinagawa H
Department of Molecular Microbiology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.
Gene. 2000 Nov 27;258(1-2):127-39. doi: 10.1016/s0378-1119(00)00416-9.
Shiga toxins 1 and 2 (Stx1 and Stx2) are encoded by prophages lysogenized in enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains. Lytic growth of the phage particles carrying the stx1 genes (stx1A and stx1B) of the EHEC O157:H7 strain RIMD 0509952, which was derived from the Sakai outbreak in 1996 in Japan, was induced after treatment with mitomycin C, but the plaque formation of the phage was not detected. We have determined the complete nucleotide sequence of the prophage VT1-Sakai. The integration site of the prophage was identified within the yehV gene at 47.7 min on the chromosome. The stx1 genes were downstream of the Q gene in the prophage genome, suggesting that their expression was regulated by the Q protein, the regulator of the late gene expression of the phage, which is similar to that of the stx1 or stx2 genes carried by the lambdoid phages reported previously. The sequences of the N gene and its recognition sites, nutL and nutR, were not homologous to those of the phages carrying the stx genes thus far reported, but they were very similar to those of bacteriophage phi21. The sequences of the repressor proteins, CI and Cro, that regulate expression of the early genes had low similarities with those of the known repressors of other phages, and their operator sequences were different from any sequence reported. These data suggest that multiple genetic recombination among bacteriophages with different immunities took place to generate the prophage VT1-Sakai. Comparison between the sequences of VT1-Sakai and lambda suggests that the ancestor of VT1-Sakai was produced by illegitimate excision, like lambda gal and bio phages.
志贺毒素1和2（Stx1和Stx2）由整合在肠出血性大肠杆菌（EHEC）O157:H7菌株中的前噬菌体编码。携带源自1996年日本阪井疫情的EHEC O157:H7菌株RIMD 0509952的stx1基因（stx1A和stx1B）的噬菌体颗粒经丝裂霉素C处理后诱导裂解生长，但未检测到噬菌体的噬菌斑形成。我们已经确定了前噬菌体VT1 - 阪井的完整核苷酸序列。前噬菌体的整合位点在染色体上47.7分钟处的yehV基因内被鉴定出来。stx1基因在前噬菌体基因组中位于Q基因的下游，这表明它们的表达受Q蛋白调控，Q蛋白是噬菌体晚期基因表达的调节因子，这与先前报道的λ样噬菌体携带的stx1或stx2基因的情况相似。N基因及其识别位点nutL和nutR的序列与迄今为止报道的携带stx基因的噬菌体的序列不同源，但它们与噬菌体phi21的序列非常相似。调节早期基因表达的阻遏蛋白CI和Cro的序列与其他噬菌体已知阻遏蛋白的序列相似度较低，并且它们的操纵序列与任何已报道的序列都不同。这些数据表明，具有不同免疫性的噬菌体之间发生了多次基因重组以产生前噬菌体VT1 - 阪井。VT1 - 阪井和λ序列之间的比较表明，VT1 - 阪井的祖先像λ gal和bio噬菌体一样是通过非法切除产生的。
