FIGURE 3.

Construction of a reporting system using pRS551-pagP. S. typhimurium 14028, SL1344, and mutants were transformed with the pRS551-Lactose operon plasmid having the Salmonella pagP promoter. The pagP promoter region containing the EcoRI and BamHI sites was generated with primers pagF and pagR. It was then amplified by PCR and inserted into pRS551, a tightly regulated expression vector with low copy number that was digested with EcoRI and BamHI. The lacZ gene is controlled by the pagP promoter. The activity of β-galactosidase was determined by using a standard assay.