Figure 1

RovM controls bacteria motility by directly regulating flhDC expression. (a,b) RovM enhances the expression of the flhDC operon. The relative expression measured by quantitative RT-PCR (a) or the β-galactosidase activity (b) in the indicated bacterial strains was determined. (c) RovM binds the flhDC promoter. Biotin-labelled probe, unlabelled probe or an unrelated fragment was incubated with RovM [0, 0.13, 0.27, 0.54 and 0.108 µM] or BSA [5 µM]. The protein-DNA complexes were detected by streptavidin-conjugated HRP and chemiluminescent substrate. Unlabelled promoter was added to determine the binding specificity of RovM. Bio-P _flhDC : biotin-labelled flhDC promoter; P _flhDC : unlabelled flhDC promoter; URD: unrelated fragment (uncropped version was shown in Fig. S4a). (d) Identification of the RovM-binding site within the flhDC promoter using a DNase I footprinting assay. (e) Nucleotide sequence of the flhDC promoter region. Putative −35 and −10 elements of the flhDC promoter are boxed. +1 denotes the transcription start point. The RovM-binding site identified with the DNase I footprinting assay was indicated by shading. (f) Motility of the Y. pseudotuberculosis YPIII, ΔrovM mutant, ΔrovM(rovM) and ΔrovMΔflhDC(rovM) strains on semi-solid plates. Data shown are the average of three independent experiments; error bars indicate SD from three independent experiments. **P < 0.01; ***P < 0.001.