FIG. 5.

Overexpression of the M. tuberculosis RelE homologs confers increased in vitro persistence to specific drugs. Mycobacteria harboring pTE-mcs-1, pTE-RelE1, pTE-RelE2, or pTE-RelE3 were grown to early log phase, and expression of toxins was induced by addition of Atc. After 4 days, the cultures were diluted to an OD₆₅₀ of 0.02 to 0.03 in medium containing Rif (4 μg/ml), Gm (10 μg/ml), Levo (10 μg/ml), or INH (1 μg/ml). Persisters were harvested by centrifugation 7 days thereafter, washed, and plated for CFU analysis. Percent survival was measured as the number of CFU/ml in the culture after incubation with the drug relative to the number of CFU/ml in the culture before the addition of drug. Fold increase values are the ratios of RelE1, RelE2, or RelE3 survivors to “vector-only” survivors. The results shown are from one of three independent experiments.