FIG 7.

Role of Fur, CcpA, CodY, and SigL in the cysteine-dependent repression of toxin production. Strains JIR8094, JIR8094::codY, and JIR8094::ccpA (A) and strains 630Δerm, 630Δerm::fur, 630Δerm::sigL, and 630Δerm::sigL(pDIA6309-sigL) (B) were grown for 10 h in PY or PYC. TcdA production was estimated from crude extracts by dot blot analysis using an anti-TcdA antibody. The results are representative of at least three independent experiments. (C) Effect of cysteine on tcdA, tcdB, and tcdR transcript levels in 630Δerm::sigL (white boxes) or 630Δerm::sigL complemented with pDIA6309-sigL (black boxes) versus the wild-type strain, 630Δerm. All strains were grown for 10 h in PYC. qRT-PCR results are presented as the ratio between the amount of the mRNA (arbitrary units) of each gene normalized by the DNA Pol III gene in both 630Δerm::sigL and 630Δerm::sigL complemented with pDIA6309-sigL compared to the mRNA level in the wild-type strain. Data are the averages from at least three independent experiments, and error bars are the standard deviations from the mean values. The statistical analysis was performed by using a t test for all genes, with the exception of tcdB (Mann-Whitney test).