FIG. 3.
The induction of rhlA by PQS and RhlR is dependent on pqsE. P. aeruginosa strains PAO-JP2 (lasI rhlI) and PAO-JP2E (lasI rhlI pqsE) carrying a plasmid harboring a rhlA′-lacZ fusion and tacp-rhlR were grown in PTSB medium supplemented with the indicated concentrations of C4-HSL in the presence (hatched bars) or absence (black bars) of 20 μM PQS, which is within the range normally produced by wild-type cultures. After 18 h of incubation at 37°C, each culture was assayed for β-Gal activity. β-Gal activity is presented in Miller units as the mean ± SD of results from duplicate assays from at least three independent experiments.