FIG 3.

Allelic exchange of rsdA and sigD in M. tuberculosis. (A and B) Targeted allelic exchange strategy for replacement of sigD (A) or rsdA (B) with a hygromycin resistance cassette flanked by loxP sites. (C) Southern blot analysis of M. tuberculosis chromosomal DNA was used to confirm the genotype of ΔsigD and ΔsigD Δrip1 strains. Hybridization of the 3′ flanking region of SigD to SmaI-fragmented genomic DNA produces a 941-bp hybridization product in the wild type, whereas the ΔsigD mutant produces a 2,972-bp hybridization product. (D) When probed with the 5′ flanking region of rsdA, BamHI-digested chromosomal DNA produces a 1,148-bp hybridization product, whereas a ΔrsdA strain produces a 7,288-bp hybridization product.