TABLE 2.

Effects of iron on abundance of tox, sigB, and dtxR transcripts in wild-type and dtxR mutant strains of C. diphtheriae^a

Strain	Value for transcript:
	tox			sigB			dtxR
	Low Fe	High Fe	Repression ratio	Low Fe	High Fe	Repression ratio	Low Fe	High Fe	Repression ratio
wt	13 ± 6	0.73 ± 0.7	19-37	0.67 ± 0.4	0.58 ± 0.3	0.8-1.5	2 ± 0.8	1.9 ± 0.5	0.9-1.5
UP	41 ± 51	7 ± 11	4-30	0.80 ± 0.5	0.83 ± 0.3	0.6-1.1	1.7 ± 0.3	1.6 ± 0.4	0.7-1.2
IN	34 ± 21	29 ± 18	0.7-1.7	1.1 ± 0.5	1.0 ± 0.5	0.7-1.7	1.8 ± 0.8	1.7 ± 0.7	0.7-1.5
ΔdtxR	40 ± 10	47 ± 21	0.6-1.2	1.1 ± 0.5	0.90 ± 0.5	0.5-1.7	3.2 ± 0.8	4.1 ± 1.1	0.5-1.2

^aThe strains from which RNA was isolated are listed in the stub: wt, C7(β); UP, C7(β)dtxR-TnUP; IN, dtxR-TnIN; ΔdtxR, C7(β)ΔdtxR. The level of each transcript was normalized to the level of the sigA transcript under high- or low-iron growth conditions (as described in Materials and Methods), and the data shown are the means and standard deviations for samples isolated from three independent cultures on the same day. The standard deviation of replicate reactions performed with the same input RNA was less than 2%, so the error introduced by the qRT-PCR assay itself was negligible. The range is shown for the repression ratios (low-iron/high-iron) among the three independent cultures.