FIG 5.

A. baumannii with oxyR inactivated is preadapted to H₂O₂ stress during exponential growth. (A) Mid-exponential-phase cultures of WT A. baumannii and the ΔoxyR strain were treated with bolus doses of H₂O₂ at the indicated concentrations for 30 min. CFU enumerated following bolus exposure are shown on a log₁₀ scale. The limit of detection was 2 log₁₀ CFU. Asterisks indicate significant differences (*, P < 0.05; ***, P < 0.001) by t test. Bars indicate means ± standard deviations. (B) qRT-PCR quantification of the relative abundances of H₂O₂-responsive transcripts in WT A. baumannii and the ΔoxyR strain in LB alone. FC, fold change. Asterisks indicate significant differences (*, P < 0.05; **, P < 0.01) by t test against a theoretical value of 1.0. Six biological replicates were run. Results are means ± standard deviations. For panels A and B, data are from a single experiment performed in biological triplicate and are representative of five independent experiments. (C) Mid-exponential-phase cultures of the A. baumannii WT and ΔoxyR strains were pretreated with 1 mM H₂O₂ or a vehicle for 30 min. Following pretreatment, cultures were exposed to a bolus of 60 mM H₂O₂ for 10 min. CFU enumerated following bolus exposure are shown on a log₁₀ scale with the limit of detection at 2 log₁₀ CFU. Asterisks indicate significant differences (*, P < 0.05; ***, P < 0.001) by one-way analysis of variance with Tukey’s multiple-comparison test. ns, no significant difference. Bars indicate means ± standard deviations.