Fig. 1.
A. Schematic representation of the pqs locus in P. aeruginosa PAO1 wild type and the IPTG-inducible pqsE strain, pqsEind. The Ω interposon (SmR/SpcR) is from plasmid pHP45Ω: the lacIQ repressor is derived, together with the Ptac promoter, from plasmid pME6032. B. Activity of the PpqsA::lux promoter fusion. The activity of the PpqsA promoter was monitored during growth in PAO1 wild type, pqsEind, rhlR and pqsEind rhlR double mutants. The maximal expression levels reached during the late exponential phase of growth are shown. Where indicated (+), 1 mM IPTG was added to the growth medium. Error bars are calculated from three independent experiments. C. Concentration of HHQ (grey bars) and PQS (white bars) determined by LC-mass spectrometry in PAO1 wild type and the pqsEind mutant. The AQs were extracted from overnight cultures grown in LB broth; where indicated (+), 1 mM IPTG was added to the growth medium. The average of the results from three independent experiments is shown and error bars represent two standard deviations from the mean.