Effects of variations in wild type or variant XylS expression on Pm activity. Upper host ampicillin tolerance levels as a function of the expression level of wild type XylS (pFZ2B1) or variant StEP-13 (pFZ2B1.StEP-13), using two different copy number variants (pFS15 and pFS15.271) of the target plasmid. Pm activity was measured as upper relative ampicillin tolerance on agar medium. The tolerance for cells containing pFZ2B1 + pFS15, no cyclohexanone, was arbitrarily set to 1 and corresponds to about 650 μg mL-1 ampicillin resistance. The relative XylS expression was measured as luciferase activity and was also set to 1 for the same data point. The data points indicate the highest ampicillin concentration on which growth occurred, while the lowest concentration on which no growth was observed is indicated by error bars. Shapes that are half grey and half black indicate identical data points for both wild type and StEP-13. 1 mM m-toluate was added to all samples, cyclohexanone concentrations leading to the measured XylS expression levels (from left to right): 0, 0.25, 0.5, 1 and 2 mM, respectively.
Zwick et al. BMC Microbiology 2013 13:262 doi:10.1186/1471-2180-13-262