Fig. 2. MntR deficiency results in sensitivity to high Mn concentrations in Mtb.

(A) Exponential growing cultures of wild type (filled bars) and mntR mutant (open bars) were diluted to a starting O.D 540 of 0.05 and exposed to increasing concentrations of metal ions. Shown is the O.D 540 of four-day cultures exposed to 200 µM of the various metal ions. Except for Mn²⁺, higher concentrations of other metals did not affect the mutant more than the wild type (data not shown). (B) Growth of M. tuberculosis strains under different manganese conditions. Wild type (squares), mntR mutant (triangles) and the complemented strain (circles) were grown in low Mn²⁺ minimal media (filled symbols) or medium containing 200µM MnCl₂ (open symbols). Growth was monitored by the increase in O.D 540 nm. Data are expressed as the mean ± standard deviations from three biological replicates.