Cloning and Sequencing of vt2 A and B Subunit of Bacteriophage Isolated from E.coli O157：H7
Abstract: According to the nucleotide sequences of the vt1 and vt2 toxin genes in GenBank, four pair of primers were designed and synthesized. vt1 and vt2 were detected in E.coli O157:H7 strains. Bacteriophage was induced and released from the strain only carrying vt2. Phage DNA was extracted and used as PCR template for the detection of the vt2, vt2-A and vt2-B genes. The purified vt2-A and vt2-B fragments were inserted into pMD18-T vector. Sequencing proved that two sequences were genes of subunit A and B of vt2. The homologies of two sequences compared to their corresponding sequences coding VT2 toxin in GenBank (accession numbers X07865, NC_002655, BA000007, AF291819) were 98%~99%, 96%~100%,respectively. Our results revealed that vt2 gene was encoded by bacteriophage, which provides a foundation for further research on horizontal transmission of VT phage carrying virulent gene.