FIG 4.

Disturbing the MexZ interaction with ArmZ decreases the extent of ArmZ-mediated induction of mexXY expression in P. aeruginosa. (A and B) RT-qPCR analysis of the expression of mexY (A) and armZ (B) by the indicated PAO1161 strains grown in L broth with or without 4 μg ml⁻¹ tetracycline. (C and D) RT-qPCR analysis of the expression of mexY (C) and armZ (D) in the WT PAO1161 and mexZ mutant strains containing either araBADp (control) or an araBADp-armZ cassette inserted at a neutral site. Cells were grown in L broth containing 0.15% arabinose to induce expression from the araBADp promoter. Data in panel D are presented on a logarithmic scale. All RT-qPCR data represent means ± SD from at least three biological replicates. Expression levels were normalized to the value for the nadB gene and are presented relative to value for the PAO1161 WT strain not exposed to tetracycline (A and B) or the PAO1161 araBADp strain (C and D). *, P < 0.05 (as determined by two-sided Student’s t test assuming equal variance); NS, not significant (P value of >0.05). ND, not detected.