FIGURE 8.

Growth characteristics and cording properties of cpsA1 and cpsA2 knock-out mutants of M. tuberculosis H37Rv mc²6206. A, evidence for allelic replacement at the cpsA1 and cpsA2 loci of M. tuberculosis H37Rv mc²6206. The WT 2,175-bp amplicon is replaced by a 4,241-bp PCR fragment in the cpsA1 mutant due to the replacement of 158 bp of the cpsA1 ORF flanked between two AfeI restriction sites with a 2-kb streptomycin resistance cassette. The replacement of the entire cpsA2 gene by a 1.2-kb kanamycin resistance cassette results in the replacement of the WT 3,734-bp amplification signal by a 3,420-bp fragment in the mutant. B, growth characteristics of the cpsA1 and cpsA2 mutants of M. tuberculosis H37Rv mc²6206 WT, the WT parent strain, and the complemented cpsA1 mutant, M. tuberculosis H37RvΔcpsA1/pMVGH1-cpsA1. The strains were grown in 7H9-ADC-Tween 80 broth at 37 °C with shaking. C, cording properties of the cpsA1 and cpsA2 mutants of M. tuberculosis H37Rv mc²6206. Shown are Ziehl-Neelsen smears of 37 °C 7H9-ADC-tyloxapol cultures. Scale bar, 50.2 μm.