Figure 7. P. mirabilis hfq was required for the RpoS level and RpoS-expressing plasmid fails to rescue hfq mutant from the H₂O₂ killing in the stationary phase.

(A) The level of rpoS mRNA in wild-type, hfq mutant and Hfq-complemented strain. The amounts of rpoS mRNA from overnight cultures of wild-type, hfq mutant and Hfq-complemented strain were quantified by real-time RT-PCR. The value of the wild-type was set at 100%. (B) The survival of wild-type, hfq mutant, rpoS mutant, RpoS-complemented strain and hfq mutant with the RpoS-expressing plasmid after exposure to H₂O₂. The H₂O₂ survival was determined as described in Fig. 3A except that overnight cultures was used instead of cultures of the exponential phase. All the data represent the average of three independent experiments with standard deviation. wt, wild-type; hfq, hfq mutant; hfqc, Hfq-complemented strain; ropS, rpoS mutant; rpoSc, RpoS-complemented strain; hfq-pRpoS, hfq mutant with the RpoS- expressing plasmid.