FIG. 3.

Induction of Cpx by alkaline pH is CpxP independent. β-Galactosidase activities were determined for PAD282 (lanes 1 and 2) and PAD488 (lanes 3 and 4) in LB broth buffered with sodium phosphate to pH 5.5 (gray bars) and 8.5 (black bars). Under noninducing conditions, β-galactosidase activity is increased approximately twofold in the cpxP null strain compared to that of the wild type (WT), reflecting the role of CpxP as a negative regulator under noninducing conditions (compare lanes 1 and 3). The cpxP null strain is induced to levels comparable to that of the wild-type strain (compare lanes 2 and 4). All strains were grown as described in Materials and Methods.