FIG 2.

Succinate oxidation is essential for the optimal growth of M. tuberculosis but is dispensable for survival under nutrient starvation. (A to E) Growth profiles of M. tuberculosis single and multiplexed sdhA1, sdhA2, and frdA knockdown strains in 7H9 medium supplemented with 30 mM succinate (A), 0.2% acetate (B), 0.2% glycerol (C), 20 mM glucose (D), or a combination of 0.1% acetate and 10 mM glucose (E). Cultures were grown in 10-mL volumes from a starting OD₆₀₀ of 0.005, and gene knockdown was induced at time zero with ATc (100 ng/mL). An mmpl3 knockdown strain was included as a positive inhibition control. The means and standard deviation for three replicates are shown. Each experiment was repeated twice. (F and G) Consequences of the single (F) or multiplexed (G) depletion of Sdh1, Sdh2, or Frd for the survival of M. tuberculosis under a nutrient starvation model of nonreplicating persistence. Before entering nutrient starvation, cells were predepleted of SDH and FRD enzymes by inducing transcriptional repression of target genes for 8 days. Cultures were then harvested, washed twice in PBS, and nutrient starved by inoculation into inkwells containing PBS plus tyloxapol. Viability was measured by enumerating CFU per milliliter over 8 weeks. Error bars represent the standard deviation from three replicates.