Fig. 3: NsrP binds to purD mRNA and negatively regulates its stability in NMEC.

a Schematic of the structure of purDH-lux. The region of the purDH promoter and the expected full-length purDH without termination codon were cloned and inserted into pMS402 to construct a purDH-lux fusion. Point mutations to generate the disrupted alleles in the purD^mutH transcript are indicated. b, c Quantification of the PurD (b) or PurD^mut (c) protein expression level in the ΔNsrP-purDH-lux strain (b) or ΔNsrP-purD^mutH-lux strain (c) by measurement of luminescence. The ΔNsrP-purDH-lux and ΔNsrP-purD^mutH-lux strains were transformed with the expression construct pNM12 (Control), or pNM12 encoding NsrP or NsrP^mut. d qRT-PCR analysis of purD expression in rifampicin-treated the WT and ΔNsrP strains. e Graphical presentation of proposed interaction of NsrP sRNA with the purD mRNA, and of base-pair changes to generate NsrP^bind-mut and PurD^syn-mut. f–i Bacterial counts in the blood (CFU/mL, f, h) and meningitis development (g, i) were determined 4 h after intravenous injection of 1 × 10⁶ CFU of the WT, NsrP^bind-mut, and ΔNsrP strains (f, g) or WT, PurD^syn-mut, ΔNsrP, and PurD^syn-mutΔNsrP strains (h, i) (n = 8 for each group in f, h). CSF culture positivity was defined as meningitis. In b–d, data were presented as the means ± SDs (n = 3 independent experiments). ns nonsignificant. One-way ANOVA (b–d), and two-tailed Mann–Whitney U-test (f, h) were applied.