FIG. 4.

qRT-PCR analysis of cprA, cprB, cprC, cprK, and CD1348 expression during growth in nisin. C. difficile wild-type (JIR8094), MC119 (cprK W235C), MC141 (cprA::intron::ermB), and MC146 (cprA::intron::ermB, PcprABC) strains were grown in BHIS supplemented with 0, 10, or 20 μg/ml nisin to an OD₆₀₀ of 0.4 as indicated. RNA was harvested, cDNA synthesized, and qPCR performed using gene specific primers for cprA (A), cprB (B), cprC (C), cprK (D), and CD1348 (E). Results were normalized to an internal control gene (rpoC) and are presented as the ratio of each transcript level relative to wild-type and no-nisin controls. The means and standard deviations of biological replicates are shown (*, P ≤ 0.05 by Student's t test).