Fig. 3.

Schematic view and characterization of ampicillin resistance phenotype in E. coli clones harboring plasmids with different dual UTR constructs. The inducible XylS/Pm promoter system (indicated by an arrow) drives the expression in all constructs. The dual UTR consists of a Tr-UTR, a spacer region and a Tn-UTR (a). The ampicillin resistance phenotype of the E. coli clones harboring each of the 25 dual UTR combinations were characterized using 2 mM m-toluic acid to provide full induction (b). Ampicillin concentrations used were ranging from 10 mg/l to 13 g/l. Results are presented as averages of the highest ampicillin concentrations at which growth was observed. Error bars point to the next tested ampicillin concentration at which no growth was observed.