Construction of a recombinant vector for site-directed mutagenesis in Salmonella typhimurium

Among all common techniques in site directed mutagenesis, Lambda Red recombinase system has been widely used to knock out chromosomal genes in bacteria. In this method, there is always the risk of DNA Linear digestion by host's restriction enzymes that leads to the low frequency of recombination. To overcome this, we constructed a recombinant vector to disrupt phoP gene in Salmonella typhimurium. The SOEing PCR method and restriction enzymes were used to construct the vector. The resulting plasmid, pTAAZ92, contains a Kanamycin cassette with two long homologous arms flanking of the phoP gene. After electrotransformation of the pTAAZ92 into the Salmonella typhimurium, the phoP gene is replaced by the Kanamycin cassette through homologous recombination. According to the high homology of the phoP gene in many of Salmonella species the pTAAZ92 can be used to disrupt the phoP gene in most of these species