Bacterial strains IMSS-II ( Salmonella serovar Typhi IMSS-1 harboring plasmid pFMTrc12 ) and IMSS-III ( Salmonella serovar Typhi IMSS-1 harboring plasmid pFMTrcleuO-50 ) were independently transformed with fusions of each of the LeuO-regulated genes ( pKK232-9 [ STY3070 ] , pKK232-9 [ assT ] , pKK232-9 [ ompS1 ] , pKK232-9 [ ompS2 ] , pKK232-9 [ tpx ] , pKK232-9 [ ompX ] , and pKK232-9 [ STY1978 ] ) to generate individual strains containing the LeuO regulator , as well as the promoter region of the LeuO-dependent gene .