FIGURE 4.

Copper stress experiments with M. bovis AF2122/97. Copper stress experiments were performed on M. bovis AF2122/97 WT, ΔTbD1, and ΔTbD1:TbD1 strains to assess the ability of TbD1 mutants to survive at high concentration of Copper ions. Two hundred micromolars of CuSO₄ was added into standing cultures for 10 days without agitation and then cultures were plated on 7H11 plates with trace amounts of Copper. CFU were then counted after 2–3 weeks of incubation and survival percentages were determined relative to the non-CuSO₄ control. The data are shown as means ± SD and are representative of three independent experiments. Statistical significance of differences in survival percentages calculated using one-way ANOVA followed by the Dunnett’s post hoc test for multiple-comparisons (*p < 0.05; ^***p < 0.001).