RT-PCR amplification of the rdxA, frxA, and ureB gene segments from total RNA of strains 26695 and SS1. Ten nanograms of total RNA was used in each RT-PCR. Plus and minus signs indicate products from cells grown with and without MTZ, respectively, as detailed in Materials and Methods. The primers used are as follows: 1, ureB-F; 2, ureB-R; 3, frxRT-F; 4, frxRT-R; 5, rdxRT-F; 6, rdxRT-R; 7, frxRT-F2; 8, frxRT-R2; and 9, rdxRT-R2 (for sequences, see Table 1). The two pairs of primers indicated were used together in each RT-PCR or PCR. Lanes showing products made in control PCRs, using genomic DNAs as a template and Taq polymerase, are marked “Genomic DNA.”