FIG. 2.
The M. tuberculosis RelE homologs are metabolic toxins. (A) Toxicity assays with E. coli. E. coli BL21(λDE3)/plysS was transformed with plasmids expressing RelE1, RelE2, or RelE3 alone or coexpressed with their cognate antitoxins. Expression of toxins was induced with IPTG, with spotting of induced or noninduced cultures 3 h thereafter. (B and C) Growth inhibition by overexpression of RelE toxins in M. tuberculosis. Expression of RelE toxins in M. tuberculosis was induced by addition of Atc at a final concentration of 50 ng/ml. Viability of cells overexpressing RelE1 (triangles), RelE2 (inverted triangles), or RelE3 (diamonds) or vector-only controls (squares) was evaluated by measuring cell density at various OD650 (B) or CFU enumeration on 7H11 agar (C). The results shown are from one of three independent experiments.