FIG. 4.
Effect of the rsd mutation on ompF promoter-directed transcription. Cells were grown in LB medium. Growth (circles) was monitored by measuring turbidity, while β-galactosidase activity (triangles) was determined at the indicated times. Expression of ςS was induced by adding arabinose (0.02%) at the middle of the exponential phase. All E. coli strains carried the ompF-lacZ fusion integrated in the genomes. (A) Strain MH513 [MH20 λ(ompF-lacZ); open symbols], its isogenic rpoS mutant, MJ83 [MH20 rpoS::Km λ(ompF-lacZ); solid symbols], and an rsd mutant, MJ57 [MH20 rsd::Km λ(ompF-lacZ); crosses]. (B) MJ513(pACYC184; open symbols), MJ57(pACYC184; solid symbols), and MJ57(pACYCRsd; crosses). (C) MH513(pACYC184; open symbols) and MH513(pACYCRsd; solid symbols). (D) MH513(pBAD22A; open symbols) and MH513(pBF1; solid symbols).