Expression of the Lactose Transposon Tn951 in Escherichia coli, Proteus and Pseudomonas

Abstract
The control of .beta.-galactosidase specified by the lactose transposon Tn951 (inserted into RP1 to give pGC9114) was studied in E. coli K12, P. mirabilis, Pseudomonas aeruginosa and P. putida; in the first 2 spp. comparison could be made with Flac. In E. coli K12, the Tn951 and chromosomally encoded enzymes showed marked qualitative differences in regulation, the former giving a substantially lower maximum induced level and induction ratio. Several parameters were slightly affected by strain background. In P. mirabilis, .beta.-galactosidase control determined by both Flac (in accord with earlier work) and pGC9114 was markedly different from E. coli in that maximal induced levels were about an order of magnitude lower and the induction ratio was reduced to 3-5. In P. aeruginosa and P. putida, Tn951-specified lac expression was qualitatively similar to that in P. mirabilis. Possible reasons for anomalous expression in Proteus and Pseudomonas are discussed.

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