Fig 4.

The antinitrosative role of DksA is independent of Hmp. (A) Transcription of the hmp::lacZY transcriptional fusion 1.5 h after wild-type (WT) and isogenic ΔdksA mutant Salmonella strains were treated with 250 μM spermine NONOate (sNO). The data are presented as Miller units (M.U.) ± standard errors of the means (SEM) of four observations collected in two independent experiments. The addition of 5 mM DETA NONOate (dNO) completely inhibited the growth of hmp-deficient Salmonella for 48 h. Consequently, 1 mM DETA (control) (B) or dNO (C) was instead tested in these experiments. At this concentration of dNO, ΔdksA mutant Salmonella strains were slightly more susceptible than the WT controls. Data represent the means of six independent observations obtained from two separate experiments. The P value for the difference between the ΔhmpA and ΔdksA::cm ΔhmpA mutant strains was <0.0001 as revealed by one-way ANOVA of all data points in the curve followed by Bonferroni's posttest.