pMB9 plasmids bearing the Salmonella typhimurium his operon and gnd gene

A plasmid containing the entire Salmonella typhimurium his operon was constructed from plasmid pMB9 and an EcoRI fragment of φ80 his immλ DNA. The recombinant pST41 also includes the gluconate 6-phosphate dehydrogenase ( gnd) gene and has one EcoRI endonuclease cleavage site in the integrated fragment. This plasmid served as a source for the construction of two additional plasmids, one carrying the OGD ▪-region of the his operon and the other a ▪ BHAFIE segment of the his gene along with the gnd gene. The presence of the his operon in the constructed plasmids was confirmed by hybridization to S. typhimurium his RNA. The location of the gnd gene in the ▪ BHAFIE fragment of the his gene was confirmed genetically: after transfection with the plasmid bearing the gnd gene, a gnd recipient gained the capacity to utilize gluconate as a sole carbon source. The DNAs of the three hybrid plasmids were analyzed by gel electrophoresis. By comparing the EcoRI endonuclease cleavage pattern of these three hybrid plasmids with the DNA cleavage pattern of φ80 his immλ, φ80 immλ and λ phages, the EcoRI cleavage map of φ80 his immλ was obtained.