Figures & data
Figure 1. Phylogenomic analysis of convergent rpoB non-RRDR mutations. Left, maximum likelihood of 98 M. tuberculosis isolates. Right, mutation profile of the rpoABC operon. The RRDR region and resistance-conferring mutations are highlighted in red. Convergent mutations independently emerging at least three times are in green. Compensatory rpoA/C mutations reported previously are highlighted in green.
Table 1. Rifampicin MICs for strains of M. smegmatis mc2155.
Figure 2. Colony morphology of wild-type and mutant M. smegmatis strains after growing on 7H10 plates for 4 days.
Figure 3. (a) In vitro competitive fitness of the rpoB mutant strains in nutritionally deficient 7H9 medium. (b) Relative transcription efficiency of the mutant strains compared to the wild-type strain. The data are shown as the mean ± SD from three independent experiments. To measure the compensation effect of double mutation, the statistical differences of double mutant strains versus the S450L single mutant strain were analysed using unpaired Student's t-test, *P < 0.05, **P < 0.01, ***P < 0.001 (t = 3.036∼10.95, df = 4).
Figure 4. Structure modelling of RNAP and potential compensatory mechanisms of rpoB non-RRDR mutations. (a) Mutations spatially around the RRDR. Potential compensatory loci are coloured in blue, and rifampicin-resistant loci are shown in red. β subunit, grey; β’ subunit, yellow; σ factor, light blue. (b) Mutations located in the region interacting with the bridge helix of the β′ subunit. The template and nontemplate DNA strands are shown in green and blue, respectively. The Mg2+ ion in the active centre is shown by a gold sphere. β and β’ subunits are shown as cartoons in grey and yellow. (c) Mutations located in the interaction surface with the σ factor in the upstream edge of the nontemplate DNA channel. (d) Mutations located at the interface between the β and β’ subunits.
