FIG. 2.
Transcriptional activity of the SPI-2 effector operon promoter (PsseA) is derepressed upon deletion of hha and requires SsrB for activity. The β-galactosidase activity of a chromosomal PsseA::lacZ reporter was examined in the indicated strains during growth under (A) SPI-2-inducing conditions (LPM at pH 5.8) and (B) noninducing conditions (LB). The data are means and standard deviations (SD) from triplicate determinations from two independent experiments. (C) The β-galactosidase activity of a chromosomal PsseA::lacZ reporter was examined in wild-type Salmonella (wt), in mutants lacking the response regulator, ssrB, or the repressor, hha, and in a double mutant lacking both ssrB and hha. The data are the means and SD from triplicate determinations from two experiments. P was <0.001 for the Δhha strain compared to the wild type. RLU, relative light units; OD600, optical density at 600 nm.