Regulation of the environmental stress response and virulence of Shigella flexneri may 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 in S. flexneri could 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, in S. flexneri and to determine its functions and possible mechanism of action. Ssr54 was 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. Ssr54 expression was significantly decreased (~ 80%) under hyperosmotic conditions (680 mM NaCl), and the survival rate of the Ssr54 deletion strain increased by 20% under these conditions. This suggested that Ssr54 has 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 that Ssr54 deletion significantly decreased S. flexneri virulence. Two-dimensional gel analyses suggest that Ssr54 may modulate the expression of tolC, ompA, and treF genes, which may affect the virulence and survival of S. flexneri under osmotic pressures. Furthermore, treF expression has been shown to improve the survival of S. flexneri under osmotic pressures. These results suggest that Ssr54 has a broad range of action in S. flexneri response to hyperosmotic environmental stresses and in controlling its virulence to adapt to environmental stresses encountered during host infection.

环境应激反应和毒力的调节福氏志贺氏菌可能涉及多种信号通路；然而，这些机制尚未明确定义。在细菌中，小调节 RNA (sRNA) 调节细菌生长、代谢、毒力和环境应激反应。因此，鉴定新的功能性 sRNA弗氏沙门氏菌可以帮助阐明病原体对宿主微环境应激和相关毒力的适应。本研究的目的是确认 sRNA 的存在，SSr54， 在弗氏沙门氏菌并确定其功能和可能的作用机制。SSr54被发现可以调节高渗压下的耐受性和毒力。通过 qRT-PCR 和 Northern blotting 验证其表达，并通过 cDNA 末端 5' 快速扩增确认其基因组位置。SSr54在高渗条件下（680 mM NaCl），表达显着降低（~ 80%），并且细胞的存活率SSr54在这些条件下，缺失菌株增加了 20%。这表明SSr54已被选择用于促进宿主在高渗条件下的生存。此外，毒力评估，包括豚鼠 Sereny 测试和小鼠肺部竞争性入侵测定，表明SSr54缺失明显减少弗氏沙门氏菌毒力。二维凝胶分析表明SSr54可以调节表达托尔C、ompA， 和特雷夫基因，可能影响毒力和生存弗氏沙门氏菌在渗透压下。此外，特雷夫表达已被证明可以提高存活率弗氏沙门氏菌在渗透压下。这些结果表明SSr54具有广泛的行动弗氏沙门氏菌对高渗环境应激的反应并控制其毒力以适应宿主感染期间遇到的环境应激。