FIGURE 1.

Transfer messenger RNA (tmRNA) deficiency is detrimental under certain stress conditions. (A) Inactivation of ssrA gene (black) by insertion/deletion of Km^r (light gray). Flanking ORFs (white) and tRNA gene (dark gray) are depicted. Promoters (curved arrows), terminators (stem-loop structures) and primers used (black arrows) are shown (B) Growth curves of wild type TIGR4 (wt) strain and its tmRNA deletion mutant (ΔssrA) in THY broth at 37°C. (C) Survival of wt and ΔssrA upon treatment with 30 mM paraquat at the indicated times, after UV irradiation at the intensities indicated, or after 30 min of exposure to 20 mM of hydrogen peroxide. Survival was determined as described in Section “Materials and Methods.” Values (mean ± SD) are the average of at least three independent experiments and the means were statistically compared using Student’s t-test (^∗P < 0.05; ^∗∗P < 0.01).