Role of Salmonella Typhimurium small RNAs RyhB-1 and RyhB-2 in the oxidative stress response.

As part of the response to specific stress conditions, bacteria express small molecules of non-coding RNA which maintain cellular homeostasis by regulating gene expression, commonly at the post-transcriptional level. Among these, in Salmonella enterica sv. Typhimurium, the paralog small non-coding RNAs RyhB-1 and RyhB-2 play an important role in iron homeostasis.

Response regulator ArcA of Salmonella enterica serovar Typhimurium downregulates expression of OmpD, a porin facilitating uptake of hydrogen peroxide.

Here we demonstrate that OmpD, the most abundant porin in Salmonella enterica serovar Typhimurium, facilitates uptake of hydrogen peroxide (H₂O₂) and that its expression is negatively regulated by ArcA upon peroxide exposure. When exposed to sublethal concentrations of H₂O₂, a S. Typhimurium ompD mutant showed decreased peroxide levels compared to those observed in the wild type strain, suggesting that H₂O₂ could be channeled inside the cell through OmpD.