FIG 4 .

ClpX negatively regulates multiple stress resistances via SpxA2. The strains indicated were monitored for PB^r (A), for the T_max (B), and for resistance to the oxidizing agents paraquat (C) and diamide (D). PB^r was determined as efficiency of plating on medium lacking or containing polymyxin B (40 μg ml⁻¹) and calculated as log₁₀ (CFU_+PB/CFU_unmod). The T_max was measured by incubating strains over a 0.1°C stepwise gradient and scoring them for growth after 24 h. Resistance to paraquat and diamide was calculated as the lowest concentration of reagent that resulted in a <10% final growth yield of the treated versus untreated strain. The data shown are the means and standard errors of the means derived from duplicate determinations from at least three independent experiments (*, P < 0.05; **, P < 0.01; ns, not significant).