FIG 7.

Regulation of rpoS expression in intact biofilms by HapR, VpsR, and VpsT. (A) Western blot detection of RpoS in intact V. cholerae biofilms. The wild type and mutants were grown as indicated in Materials and Methods, and RpoS was detected by using a polyclonal antibody as previously described (32). Biofilm mass was measured by using a crystal violet assay (OD₅₇₀), and standard deviations are shown in parentheses. (B) Quantitative measurement of RpoS expression in V. cholerae biofilms. V. cholerae C7258 (wild type) and isogenic mutant strains AJB51 (ΔhapR), HX17 (ΔvpsT), HX13 (ΔvpsR), HX18 (ΔvpsR ΔvpsT), HX03 (ΔhapR ΔvpsT), and HX14 (ΔhapR ΔvpsR) containing an rpoS-luxCDABE promoter fusion were allowed to develop static biofilms in 96-well plates for 24 h at 30°C. The planktonic cells were removed, and light was measured. Light production was normalized by biofilm mass after staining of adherent cells with crystal violet. Each value represents the mean for six independent cultures. Error bars indicate standard deviations (*, significantly different from the wild type [P < 0.01]).