FIG 5.

Impaired succinate oxidation by the dual depletion of Sdh1 and Sdh2 synergizes with bioenergetic inhibitors in M. tuberculosis but attenuates the activity of cell wall inhibitors. (A to C) Effect of the joint transcriptional repression of sdhA1 and sdhA2 on the susceptibility of M. tuberculosis to the cell wall inhibitors ethambutol (EMB) (A), ethionamide (ETH) (B), and SQ109 (C). (D to H) Effect of the joint transcriptional repression of sdhA1 and sdhA2 on the susceptibility of M. tuberculosis to bioenergetic inhibitors: BDQ (D), TB47 (E), Q203 (F), clofazimine (CFZ) (G), and thioridazine (THZ) (H). (I to L) Effect of the joint transcriptional repression of sdhA1 and sdhA2 on the susceptibility of M. tuberculosis to inhibitors of transcription, translation, or DNA replication: rifampicin (RIF) (I), streptomycin (STREP) (J), linezolid (LZD) (K), and levofloxacin (LEV) (L). Cultures were predepleted of SDH enzymes by inducing gene knockdown (0 or 100 ng/mL ATc) for 6 days and then inoculated into 96-well plates at a starting OD₆₀₀ of 0.005 with 0 or 100 ng/mL ATc and a 7-point, 3-fold dilution gradient of each drug. Viability was determined after 10 days of incubation, and CFU per milliliter was enumerated after 5 weeks. Blue boxes denote concentrations above the MIC of the no-knockdown control. Dashed horizontal lines represent the upper and lower levels of detection. Results are the mean and standard deviation from three replicates and are representative of at least two independent experiments. Inoc, CFU per milliliter at inoculation (i.e., time = 0).