A Novel Srna In Shigella Flexneri That Regulates Tolerance And Virulence Under Hyperosmotic Pressure

Regulation of the environmental stress response and virulence ofShigella flexnerimay involve multiple signaling pathways; however, these mechanisms are not well-defined. In bacteria, small regulatory RNAs (sRNAs) regulate bacterial growth, metabolism, virulence, and environmental stress response. Therefore, identifying novel functional sRNAs inS. flexnericould help elucidate pathogenic adaptations to host micro-environmental stresses and associated virulence. The aim of this study was to confirm the presence of an sRNA,Ssr54, inS. flexneriand to determine its functions and possible mechanism of action.Ssr54was found to regulate tolerance and virulence under hyperosmotic pressure. Its expression was verified by qRT-PCR and Northern blotting, and its genomic position was confirmed by 5 '-rapid amplification of cDNA ends.Ssr54expression was significantly decreased (similar to 80%) under hyperosmotic conditions (680 mM NaCl), and the survival rate of theSsr54deletion strain increased by 20% under these conditions. This suggested thatSsr54has been selected to promote host survival under hyperosmotic conditions. Additionally, virulence assessment, including guinea pig Sereny test and competitive invasion assays in mouse lungs, revealed thatSsr54deletion significantly decreasedS. flexnerivirulence. Two-dimensional gel analyses suggest thatSsr54may modulate the expression oftolC, ompA, andtreFgenes, which may affect the virulence and survival ofS. flexneriunder osmotic pressures. Furthermore,treFexpression has been shown to improve the survival ofS. flexneriunder osmotic pressures. These results suggest thatSsr54has a broad range of action inS. flexneriresponse to hyperosmotic environmental stresses and in controlling its virulence to adapt to environmental stresses encountered during host infection.