Fig 4. The bd oxidase is necessary for optimal respiration under low pH conditions.

Oxygen consumption rate (OCR) was measured using the extracellular flux analyser. A) H37Rv, ΔcydA and ΔcydA::ABDC strains were exposed to media at pH 7.4 for ~30 minutes and then treated with Q203 (10nm) at the indicated time. Data are normalized to point 4. Bar graph of point 9 (black arrow). B) H37Rv was exposed to media at pH 7.4 and pH 4.5 for ~30 minutes and then treated with media, Q203 (300x MIC₅₀ 900nM), or BDQ (300x MIC₅₀ 16.2uM) followed by the uncoupler, CCCP, at the indicated times. Data are normalized to point 4. Bar graphs are plotted from point 5 and point 9 (black arrows in A) after the addition of BDQ/Q203 and before the addition of CCCP, respectively. C) OCR measurements (pmol O₂/min) of H37Rv, ΔcydA and ΔcydA::ABDC strains after ~30 minutes pre-exposure to media at pH 7.4 or pH 4.5. Bar graphs are plotted from point 4 (black arrow). Analysis was performed using a one-way ANOVA with Tukey post-test. * p-value < 0.05, ** p-value < 0.01, **** p-value <0.0001. Data depict single experiments that are representative of at least 2 independent studies.