FIG. 2.

Overproduction of β-galactosidase by E. coli CC118 with the expression systems transposed into the chromosome. (A) Coomassie blue-stained SDS-PAGE gel containing total proteins from cells expressing lacZ and containing the transposable elements of pCNB4-lacZ, pCNB2-lacZ, and pCNB4-S2/pTPm-lacZ inserted into the chromosome. Induction and lack of induction by 2 mM salicylate are indicated by plus and minus signs, respectively. Accumulation of β-galactosidase is indicated by an arrow. (B) Quantification by densitometry. The bars indicate the relative amounts of β-galactosidase (β-gal).