CrcZ relieves repression by Hfq in vivo.
(A) The esterase activity was measured as change in A410 min−1 per OD600 in strain PAO1Δcrc harboring either the control plasmid pMMB67HE (green bar) or the crcZ encoding plasmid pMMBcrcZ (pink bar). The strains were grown to an OD600 of 1 in BSM medium supplemented with 40 mM succinate. Then, crcZ expression was induced by addition of IPTG and samples were withdrawn 60 minutes thereafter. The error bars represent standard deviations from three independent experiments. The CrcZ levels (top panel) were determined by Northern-blot analysis. 5S rRNA served as a loading control. (B) The strains were grown to an OD600 of 2.0 in BSM medium supplemented with 40 mM succinate and 40 mM acetamide. Then, the cells were harvested and the β-galactosidase activities were determined. The bars depict the β-galactosidase values conferred by the translational amiE::lacZ fusion encoded by plasmid pME9655 in strain PAO1 (blue bar), PAO1ΔcrcZ (pink bar), PAO1hfq- (red bar) and PAO1hfq-ΔcrcZ (purple bar). The error bars represent standard deviations from three independent experiments.