FIG 4.
Expression of fbp and hmu operons is QS dependent. (A) fbp-lacZ expression in the wild type and the QS-defective mutants. (B) hmu-lacZ expression in the wild type and the QS-defective mutants. β-Galactosidase activity assays were performed as described previously, and data are presented in Miller units. The results are representative of three experiments. Error bars indicate standard deviations. Asterisks indicate a significant increase compared to the control in the same treatment period (*, P < 0.1; **, P < 0.05; ***, P < 0.01). (C) Gel mobility shift assays using purified PdeR-His and a DNA fragment containing the hmu promoter (P1) or fbp promoter (P2) regions. Lanes 1 and 6, a synthetic end-labeled 50-bp DNA fragment (thermal probe); lanes 2 and 7, PdeR protein did not form a complex with the labeled DNA fragment; lanes 3 and 8, the addition of C16-HSL resulted in complex formation; lanes 4 and 5 and 9 and 10, the binding specificity of PdeR for the probe DNA was not affected by unlabeled competitor DNA (cold probe).