FIG 8.

FTS_1680 is required for heat stress tolerance. (A to E) Growth curves of F. tularensis strains FSC200 (black), inFTS_1680 (light gray), and complemented inFTS_1680 (dark gray) (supplemented with kanamycin at 20 μg/ml) in Chamberlain's medium incubated at 37°C (A) or 42°C (B) or under the following stress conditions: pH 4.0 (C), 4% NaCl (D), or iron depletion (E). Bacterial growth was determined by measuring the OD₆₀₀ in pentaplicate every 10 min for 24 h. CFU were analyzed at the end of the experiment to verify OD₆₀₀ measurement. (F) Oxidative stress experiments. Stationary-phase bacteria of F. tularensis strains FSC200 (black) or inFTS_1680 (light gray) were diluted 1:10 in fresh Chamberlain's medium and exposed to 0.03% H₂O₂. CFU were determined at the start of the experiment and after 20 and 40 min. The results shown are representative of three independent experiments. Statistical significance was analyzed at the 24-h time point using an unpaired t test, ****, P < 0.0001 (comparing inFTS_1680 with the wild-type FSC200 strain); ####, P < 0.0001 (comparing inFTS_1680 with the complemented strain).