Expression of HapR and RpoS reporter lacZ fusions in V. cholerae hns mutants. (A) Strains C7258ΔlacZ (wild type [WT]), AJB80 (C7258ΔlacZ Δhns::Km), and AJB51ΔlacZ (ΔhapR) containing plasmid pLux-LacZ were grown to stationary phase (16 h) in TSB at 37°C. (B) Strains C7258ΔlacZ (WT), AJB80 (C7258ΔlacZ Δhns::Km), and AJB50ΔlacZ (ΔrpoS) containing plasmid pPerA-LacZ were grown as described above. (C) Strains C7258ΔlacZ (WT) and AJB80 (C7258ΔlacZ Δhns::Km) containing an rpoS-lacZ transcriptional fusion were grown as described above. β-Galactosidase activity was determined as described in Materials and Methods. Each value is the average for three independent cultures. Error bars, standard deviations.