FIG. 7.

Inducible production of MtrR represses rpoH expression and modulates antimicrobial susceptibility levels in gonococci. (A and B) Strain JF7 was grown in the presence or absence of 1 mM IPTG as described in Materials and Methods, and cell lysates before induction (0 Hour) or after 1 h of incubation in the absence (−) or presence (+) of IPTG were solubilized and subjected to SDS-PAGE using a 12.5% (wt/vol) SDS-PAGE gel with the separated proteins stained by Coomassie brilliant blue (A); the positions of the molecular mass markers are shown on the left of the gel, and the approximate positions of MtrR as determined by immunoblotting with detection using anti-MtrR antiserum (B) are shown. (C) Specific activity values for β-Gal levels in the control (−IPTG) and induced (+IPTG) cultures. The results are shown as average values (± standard deviations) from three independent assays. The difference was significant (P = 0.0012). (D) The efficiencies of plating of the control and IPTG-induced cultures on GCB agar with or without 0.5 μg/ml of Ery are shown. (E) The H₂O₂ susceptibilities of the control and IPTG-induced cultures were assessed by a disk diffusion assay, and the difference in growth inhibition between the cultures was significant (P < 0.001).