FIG. 6.

Complementation of ΔtlpB mutant. (A) The pRDX-C vector was constructed in pBlueScript as described in the text. A multiple cloning sequence (MCS) from the vector is flanked by the 5′ coding sequences of rdxA (I) and 3′ rdxA sequences (II). rdxA encodes an oxygen-insensitive NADPH nitroreductase that activates the prodrug metronidazole to toxic hydroxylamine adducts (10). (B) PCR validation of the TlpB complement. Amplicons were generated by PCR with primers designed to flanking sequences of tlpB (outside the promoter region and at the 3′ end) which were present in all constructs. WT = SS1 (2 kb); SS1 ΔtlpB::aphA3 (Km) (1.5 kb) and ΔtlpB/tlpB⁺ complement (doublet). MW, molecular weight.