FIG. 5.

FliZ regulates type 1 fimbrial gene expression though FimZ. (A) FliZ is unable to regulate P_fimA promoter activity in the absence of FimZ. P_fimA promoter activities in the wild type, the ΔfimZ mutant, the ΔfliZ mutant, the ΔfimZ ΔfliZ mutant, the ΔfliZ mutant expressing FliZ from the constitutive P_LtetO-1 promoter on a plasmid (pFliZ), and the ΔfimZ ΔfliZ mutant harboring pFliZ are shown. (B) FliZ regulates FimZ posttranscriptionally. P_fimA promoter activities in the P_fimZ::tetRA ΔfimY mutant, the P_fimZ::tetRA ΔfimY ΔfliZ mutant, and the P_fimZ::tetRA ΔfimY ΔfliZ mutant expressing FliZ from the constitutive P_LtetO-1 promoter on a plasmid are shown. In the genetic background P_fimZ::tetRA, FimZ is under the control of a tetracycline-inducible promoter. Overnight cultures were subcultured 1:1,000 in fresh LB and then grown statically at 37°C for 24 h. FimZ expression was induced by addition of 15 μg/ml tetracycline. Fluorescence and optical density (OD600) values were then measured for each sample. Average promoter activities from three independent experiments on separate days are reported. For each experiment, six samples were tested. Error bars denote standard deviations.