Fig. 9. Expression of H-NS and LeuO in V. cholerae biotypes.

A. Strains C7258ΔlacZ (El Tor, lane a) and O395ΔlacZ (classical, lane b) were transformed with vector pUC-rrnB-leuO-FLAG encoding a leuO-FLAG fusion expressed under its native promoter. The strains were grown in LB medium to stationary phase and the expression of LeuO-FLAG was determined by western blot. B. Strains C7258ΔlacZΔhns (AJB80, lane a), C7258ΔlacZ (lane b) and O395ΔlacZ (lane c) were grown in LB medium to stationary phase and the expression of H-NS was determined by western blot. Lanes d, e and f were loaded with 40, 80 and 160 ng of purified H-NS protein, respectively. The number of H-NS molecules per cell was estimated by densitometry and dilution plating. C. Quantitative densitometry analysis of LeuO and H-NS expression in classical and El Tor V. cholerae biotypes. V. cholerae strains of the classical and El Tor biotypes containing plasmid pUC-rrnB-leuO-FLAG were grown to stationary phase in LB at 37°C and the cells were collected for western blot analysis. Expression of LeuO-FLAG was detected using anti-FLAG M2-peroxidase monoclonal antibody (□, open bars). H-NS was quantified using a polyclonal antibody as described in materials and methods (■, filled bars). The bars indicate the average band volume (pixels) ± STDEV from four independent cultures.