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. 2018 Nov 23;9:2752. doi: 10.3389/fmicb.2018.02752

FIGURE 3.

FIGURE 3

PQS and HHQ production is impaired in the strain that overproduces the MexCD-OprJ efflux pump. (A) To determine the accumulation levels of the autoinducers synthesized by Pseudomonas aeruginosa, a technique based on TLC coupled with a PqsR-based biosensor was used. The samples were extracted from cultures in early stationary phase (OD600 = 2.5). (B) The TLC-spots corresponding to HHQ were quantified by densitometry and the ratio between the HHQ present in the supernatant respect to cell extract was calculated and represented. Statistical significances were evaluated by using a Student’s two-tailed test and considered significant if P < 0.05, with a confidence interval of 95% (∗P < 0.05; ∗∗P < 0.01; ∗∗∗P < 0.001). As shown, overexpression of the MexCD-OprJ efflux system in nfxB∗ strongly reduces the production of PQS and HHQ as compared with PAO1 and nfxB∗ΔmexD strains. Furthermore, the analysis by densitometry of the HHQ ratio shows that this defect in AQs production is likely caused by an excessive extrusion of HHQ through MexCD-OprJ.