FIG. 3.

Positive regulation of fliPQR by RcsB. (A) Schematic showing the fliL operon and rcsA. The lengths of the region corresponding to the individual genes within the operon are drawn approximately to scale with respect to each other. Arrows indicate the transcription start sites. The square box in the intergenic region between fliR and rcsA is the RcsAB box (not drawn to scale). (B) Microarray data showing positive or negative regulation of the indicated genes during mid-exponential and stationary phases of growth. QW119 is the igaA* (RcsB⁺⁺) mutant, and QW441 its isogenic ΔrcsA derivative. The data are extracted from Table S4 in the supplemental material. (C) RT-PCR results for RNA isolated from strains indicated on the left. QW556 is deleted for residues 1 to 48 in the intergenic region between fliR and rcsA, starting at the first base pair after the stop codon of fliR. Primers pairs were designed to anneal within the coding region of the genes indicated at the top. RNA for the wild-type (WT) strain was isolated at mid-log phase, at which point flagellar gene expression is maximal, while that for the igaA* strains was isolated at stationary phase, at which point the activity of the Rcs system is maximal.