FIG 6.
Effects of indole derivatives on heat tolerance of the ΔtnaA mutant. (A) The preculture of the ΔtnaA mutant was diluted in fresh TSB with indole (2.0 mM), 5-iodoindole (0.5 mM), 5-hydroxyindole (2.0 mM), or indole-3-acetic acid (2.0 mM) to obtain approximately 108 CFU/ml and subjected to heat tolerance assays (55°C, 5 min). (B) Isolated persister cells of the ΔtnaA mutant were resuspended in fresh TSB with indole (2.0 mM), 5-iodoindole (0.5 mM), 5-hydroxyindole (2.0 mM), or indole-3-acetic acid (2.0 mM) to obtain approximately 105 CFU/ml and subjected to heat tolerance assays (57°C, 5 min). Data points represent means of results from at least three independent experiments, and error bars indicate standard deviations. Significant differences among all of the data were analyzed by the Tukey’s test, and bars with different letters are statistically different (P < 0.05).