Willshaw G A, Smith H R, Scotland S M, Field A M, Rowe B
Division of Enteric Pathogens, Central Public Health Laboratory, London, UK.
J Gen Microbiol. 1987 May;133(5):1309-17. doi: 10.1099/00221287-133-5-1309.
Phages coding for production of Vero cytotoxins VT1 or VT2 in strains of Escherichia coli serotype O157.H7 or O157.H- were morphologically indistinguishable. Their genome size and restriction enzyme digests of the phage DNA were similar. These phages were clearly different in these respects from a VT1-encoding phage isolated from a strain of E. coli O26.H11 (H19). However the VT1 region cloned from the phage originating in the E. coli O157.H7 strain was identical to the VT1 region previously cloned from the phage carried by H19. Sequences encoding VT2 that were cloned from the phage in E. coli O157.H- have been mapped and the VT2 region identified by transposon insertion. The cloned regions coding for VT1 or VT2 production had no similarities in the presence of restriction enzyme sites over a distance of about 2 kb, and two VT1-specific probes spanning a region of about 1.4 kb did not hybridize under stringent conditions with cloned VT2 DNA. A 2 kb HincII fragment contained the VT2 genes but hybridized to VT1-encoding phages and recombinant plasmids via flanking phage DNA. A 0.85 kb AvaI-PstI fragment was a specific probe for VT2 sequences and did not hybridize under stringent conditions to phages or plasmid recombinants encoding VT1.
编码大肠杆菌血清型O157.H7或O157.H -菌株中Vero细胞毒素VT1或VT2的噬菌体在形态上无法区分。它们的基因组大小以及噬菌体DNA的限制性酶切图谱相似。这些噬菌体在这些方面与从大肠杆菌O26.H11（H19）菌株分离出的编码VT1的噬菌体明显不同。然而，从源自大肠杆菌O157.H7菌株的噬菌体克隆的VT1区域与先前从H19携带的噬菌体克隆的VT1区域相同。从大肠杆菌O157.H -中的噬菌体克隆的编码VT2的序列已进行图谱绘制，并通过转座子插入鉴定了VT2区域。编码VT1或VT2产生的克隆区域在约2 kb的距离内限制性酶切位点的存在上没有相似性，并且跨越约1.4 kb区域的两个VT1特异性探针在严格条件下不与克隆的VT2 DNA杂交。一个2 kb的HincII片段包含VT2基因，但通过侧翼噬菌体DNA与编码VT1的噬菌体和重组质粒杂交。一个0.85 kb的AvaI - PstI片段是VT2序列的特异性探针，在严格条件下不与编码VT1的噬菌体或质粒重组体杂交。
