中国生物工程杂志

PhoQ gene that was amplified by polymerase chain reaction(PCR)from Salmonella typhimurium genome DNA was cloned into a procaryotic expression plasmid pUC18, sequenced and GenBank accession No. is DQ787014. The identified recombinant plasmid was then used to transform into the competent Salmonella, and the positive clones were screened by PCR and restriction enzyme digestion.and phoQ recombinant protein was expressed by IPTG induced method. PhoQ gene expression was analyzed by SDS-PAGE. The stability of recombinant bacterial cultured in vivo was observed. It showed t hat recombinant bacterium could stably reproduction, growth and hand down from generation to generation in vivo. To investigate the effects of different virulence of the recombinant S. typhimurium and wildness S. typhimurium, which were tested in 45 days old asepsis' KM mice by nonnasality rejection. The data showed that the LD50 of the recombinant and wildness strains were 3.981×107 cf u/ mL and 5.012×102 cf u/ mL ,respectively. It suggests that the different virulence between the two strains were occurred, the wildness S. typhimurium was more virulent than the recombinant S. typhimurium. The result testified phoQ gene is one of the important regalatots in the virulence mechanism of S. typhimurium.