FIG 5.

Noncognate antitoxin proteins counteract the mRNA interferase activity of MazF₁^Bif. Relative transcript levels of tufA^Bif were determined in E. coli expressing tufA^Bif with pACYCDuet-1, pAD-F₁, and pAD-F₁E₂ (A) or pAD-F₁B (B). The strains were grown with 0.2% arabinose for 2 h to induce tufA^Bif expression. Then, 1 mM IPTG was added to induce MazF₁^Bif, MazF₁^Bif and MazE₂^Bif, or MazF₁^Bif and RelB^Bif expression. After 3 h, 200 μg/ml rifampin was added. Samples were collected at the indicated time points after rifampin addition and the levels of tufA^Bif mRNA were monitored by qRT-PCR (normalized to the 16S rRNA transcript level). The values presented are the averages from three independent experiments, and error bars represent the standard deviations. A two-way analysis of variance with Bonferroni posttest was used to obtain P values for each time point. ***, P < 0.001.