FIG 1.

EIIA^Ntr G expression of iron uptake genes under low-iron conditions. (A) mRNA abundance of fhuA, fepA, and iroB genes was determined in the wild-type (WT) and the ptsN mutant strains grown in acidified M9 medium (pH 5.8) to mid-log phase. (B and C) β-Galactosidase activities of Salmonella with a p_fhuA-lacZ fusion in the normal chromosomal location and isogenic ptsN mutants with denoted plasmids (empty vector [pVec] or plasmid expressing EIIA^Ntr from a heterologous promoter [pPtsN]) were determined. Bacteria were grown to mid-log phase in acidified M9 medium (pH 5.8) with 8 nM FeSO₄ and IPTG at the denoted concentrations (B) or in acidified M9 medium (pH 5.8) with FeSO₄ at the denoted concentrations (C). The means and standard deviations (SD) of results from at least three independent experiments are shown as follows: symbols or bars, mean values; error bars, SD. Two-tailed t tests were performed for comparisons between the wild-type strain and the ptsN mutant or between indicated strains, and statistical significance is indicated as follows: ns, not significant; *, P < 0.05; **, P < 0.01; ****, P < 0.0001.