FIG. 5.

Effects of an atpB null mutation and alkaline pH on the Psp, Cpx, and RpoE systems. Φ(pspA-lacZ), Φ(cpxP-lacZ), and Φ(rpoE-lacZ) operon fusion strains YVM576, AJD243, and AJD242, respectively (WT [wild type]), or their ΔatpB derivatives (Table 1) were grown at 26°C after inoculation of cultures to an initial optical density at 600 nm of 0.05. Cultures were grown in LB medium buffered to either pH 7 or 8, and samples were taken after 8 h (white bars) or 24 h (black bars) for β-galactosidase assays (Sp. Act. = specific activity; see Materials and Methods).