Transcriptional activity of prrhlG . Promoter activity was followed by measuring the luminescence from P. aeruginosa PAO1 wildtype (squares) and mutant strains, harbouring pAB134, which contains the prrhlG::luxCDABE transcriptional fusion. Activity was compared between the wildtype PAO1 strain and PAOU (algU mutant, triangles) (A); PAO1 and PAO6358 (rpoN mutant, diamonds) (B), and PAO1 and PDO100 (rhlI mutant) strain complemented with C4-HSL (open circles) or not (blacks circles) (C). Activity is expressed in Relative Units of Luminescence per 0.5 second in function of time growth. Gain for luminescence detection was automatically set for each experiment. Results are representative of 2 complete experiments and of several additional experiments with fewer time points, standard deviations were < 6% for all values. Curve without symbol in panel B: growth curve of PAO1.