Transcription from pspA-lacZ and pspG-lacZ is inhibited in ssrS1 cells through changes in PspF levels. β-Galactosidase activities of indicated promoter-lacZ fusions were measured in Miller units. (A) Expression from pspF-lacZ, pspA-lacZ, pspG-lacZ, galP2-lacZ, and λpR-lacZ was examined in wild-type (shaded bars) or ssrS1 (solid bars) strain backgrounds when strains were grown at 30°C for 18 h. Data shown are averages from at least two experiments. (B) Wild-type (KW441), ssrS1 (KW442), ΔpspF (KW443), or ΔpspFssrS1 (KW444) cells containing pspA-lacZ and either the control plasmid pKK* (open bars) or pKK-pspF* (shaded bars) were grown in unbuffered LB at 30°C for 18 h. (C) Wild-type (KW445), ssrS1 (KW446), ΔpspF (KW447), or ΔpspFssrS1 (KW450) cells containing pspG-lacZ and either the control plasmid pKK* (open bars) or pKK-pspF* (shaded bars) were grown in unbuffered LB at 30°C for 18 h. Data in panels B and C are averages of two representative experiments with three duplicates. Error bars, standard deviations from the averages.