FIG. 3.

(A) Growth curves for the wild type, the Δhfq mutant, and the Δhfq_C complemented mutant in GC medium supplemented with different concentrations of IPTG (in μM, as indicated after the mutant designation). Three independent sets of cultures were grown on different days, and the symbols indicate the average of the three cultures for each strain; the error bars show the standard deviations. The calculated generation times of the cultures were as follows: MC58, 48 ± 7 min; Δhfq, 78 ± 10 min; and Δhfq_C with 0, 1, 10, 100, and 1,000 μM IPTG, 80 ± 5, 80 ± 5, 70 ± 17, 55 ± 8, and 51 ± 10 min, respectively. (B) Western blotting and SDS-PAGE of cell lysates of the MC58 wild-type strain, the Δhfq mutant, and the complemented mutant, showing Hfq expression and pleiotropic effects of Hfq on protein expression in the Δhfq mutant. IPTG was added at the final concentrations indicated to the growth medium for induction of Hfq in the complemented mutant. Cells were grown in GC broth to an OD₆₀₀ of 0.5, and 10 μg of total protein was added to each lane. The positions of molecular weight markers are indicated on the left. The arrows on the right indicate the positions of derepressed protein bands, and the filled circles indicate downregulated protein bands in the hfq null mutant.