FIG 4.

PDF overexpression abrogates WT and ΔzntA ΔzitB mutant differences but fails to restore growth in the presence of NO·. The mean time required to reach the 50% maximum final OD₆₀₀ was measured for WT and ΔzntA ΔzitB mutant strains in the presence of various concentrations of the NO· donor SperNO. A ΔzntA ΔzitB mutant exhibited delayed exit from lag phase compared to the WT, which was abrogated by PDF overexpression (pdef). However, dose-dependent NO· inhibition of the growth of both strains was still observed. Significance was determined by an unpaired two-tailed t test. *, P ≤ 0.05; **, P ≤ 0.01; ****, P ≤ 0.0001; ns, nonsignificant (n = 9 to 15). Data are represented as means, with error bars showing standard deviations.