Effects of FNR, CRP, and H-NS on in vivo transcription of hlyE. All cultures were grown in L-broth at 37°C for ∼16 h under the indicated conditions. The activity of the hlyE promoter was estimated by measuring the β-galactosidase activity associated with each culture carrying the hlyE::lacZ plasmid pGS1629. Strains: parental, M182; fnr, JRG4747; crp, JRG4830; hns, JRG4864 (Table 1). Error bars indicate 2 standard deviations from the means (n = 3).