Nitric oxide is a host cue for Salmonella Typhimurium systemic infection in mice

Abstract

Nitric oxide (NO) is produced as an innate immune response against microbial infections. Salmonella Typhimurium (S. Typhimurium), the major causative pathogen of human gastroenteritis, induces more severe systemic disease in mice. However, host factors contributing to the difference in species-related virulence are unknown. Here, we report that host NO production promotes S. Typhimurium replication in mouse macrophages at the early infection stage by activating Salmonella pathogenicity island-2 (SPI-2). The NO signaling-induced SPI-2 activation is mediated by Fnr and PhoP/Q two-component system. NO significantly induced fnr transcription, while Fnr directly activated phoP/Q transcription. Mouse infection assays revealed a NO-dependent increase in bacterial burden in systemic organs during the initial days of infection, indicating an early contribution of host NO to virulence. This study reveals a host signaling-mediated virulence activation pathway in S. Typhimurium that contributes significantly to its systemic infection in mice, providing further insights into Salmonella pathogenesis and host–pathogen interaction.

Salmonella enterica serovar Typhimurium remodels mitochondrial dynamics of macrophages via the T3SS effector SipA to promote intracellular proliferation

“…BMDMs were infected, as previously described, with slight modifications. 48 Briefly, overnight-grown bacteria were inoculated into fresh LB medium at a ratio of 1:100 and further grown to the stationary phase until an OD 600 of 1.5. Bacteria were pelleted and opsonized in the RPMI 1640 medium supplemented with 10% FBS for 20 min at 37°C.…”

Transcriptome Analysis Reveals the Effect of PdhR in Plesiomonas shigelloides

“…Phosphorylation reactions of ArcA (ArcA-P) were carried out as described previously [55], then EMSAs of ArcA-P and each purified promoter fragment were performed by adding increasing concentrations of phosphorylated ArcA-His 6 fusion proteins in binding buffer (100 mM Tris-HCl (pH 7.5), 10 mM MgCl 2 , 2 mM DTT, 100 mM KCl, 10% glycerol) at 37 • C for 30 min, and non-phosphorylated ArcA (ArcA-P(-)) as the negative control. EMSAs of FNR and each of the purified promoter fragments were performed by adding increasing concentrations of FNR-His 6 fusion protein in binding buffer (20 mM Tris-HCl (pH 7.5), 80 mM NaCl, 0.1 mM EDTA, 1 mM DTT, and 5% glycerol) at 37 • C for 20 min [56]. Additionally, EMSAs of CRP and each purified promoter fragments in 20 µL of binding buffer (50 mmol Tris-HCl (pH 8.0), 250 mmol/L KCl, 5 mmol/L MgCl 2 , 2.5 mmol/L EDTA, 2.5 mmol/L DTT, 1 µg Poly (dI.dC) and 0.5 µmol/L cAMP) for 30 min at room temperature [57].…”