FIG. 3.

Regulation of porin and SPI2 genes in Salmonella by the hybrid sensor kinase Taz. (A) Taz regulation of porin genes behaves in Salmonella as it does in E. coli. Treatment of wild-type Taz (Taz^wt) with 1 mM aspartate increased ompC promoter activity, and there was a concomitant decrease in ompF promoter activity. The reciprocal responses of the promoters were amplified upon regulation by the constitutively active superkinase T247R mutant of Taz (Taz^c). (B) Taz regulation of SPI2. The ssrA promoter was upregulated in the presence of aspartate or the superkinase, but these conditions were not sufficient for activation of expression from the ssaG promoter. The error bars indicate standard errors (n = 3), and the P values are the result of unpaired t tests assuming unequal variances.