FIG 4.
mRNA levels of iron transport genes in response to pH changes. Quantitative PCR was used to measure relative levels of mRNA isolated from wild-type bacteria grown to mid-logarithmic phase and exposed to iron starvation stress through the addition of the iron chelator EDDA. The level of feoB, fbpA, vctP, and vibB mRNAs was assessed. The data represent the means and standard deviations from biological triplicates. *, P < 0.05; **, P < 0.01; and ***, P < 0.0001, as determined by two-way analysis of variance, Holm-Šidák multiple-comparison test for ΔCT values.