PmrA decreases expression of the SPI-2 ssaG gene. (A) Fluorescence from a ssaG-gfp transcriptional fusion was determined in wild-type, pmrA, and ssrB Salmonella grown in N-minimal medium at pH 4.6 with 1 mM Mg2+ (LH) or 10 μM (LL), or pH 7.7 with 1 mM Mg2+ (HH) or 10 μM (HL) for 8 h. (B) Relative expression from a chromosomal ssaG-lacZ transcriptional fusion was determined in wild-type, pmrA, pmrA harboring the plasmid vector (pUHE21-2lacIq), and pmrA harboring a plasmid expressing pmrA from a lac promoter derivative following growth in N-minimal medium at pH 4.6 with 1 mM Mg2+ (LH). Values are normalized relative to those displayed by the wild-type strain. (C) mRNA levels of ssaG produced by wild-type, pmrA, and ssrB Salmonella grown overnight in LB media (inoculum) and 4 h after infection of J774A.1 macrophages.