Wang Ligui, Yang Guang, Qi Lihua, Li Xiang, Jia Leili, Xie Jing, Qiu Shaofu, Li Peng, Hao RongZhang, Wu Zhihao, Du Xinying, Li Wuju, Song Hongbin
Institute of Disease Control and Prevention, Academy of Military Medical SciencesBeijing, China; Center of Computational Biology, Beijing Institute of Basic Medical SciencesBeijing, China.
Institute of Disease Control and Prevention, Academy of Military Medical Sciences Beijing, China.
Front Cell Infect Microbiol. 2016 Mar 8;6:24. doi: 10.3389/fcimb.2016.00024. eCollection 2016.
Shigella flexneri is an important cause of bacillary dysentery in developing countries. Small regulatory RNAs (sRNAs) play essential roles in diverse cellular processes. We found a novel sRNA Ssr1 based on RT-PCR, northern blot, and 5'RACE in S. flexneri. Ssr1 responds to acidic environmental changes, as shown by a strong linear correlation between the pH value and Ssr1 expression (R = 0.785, P < 0.05) using the qRT-PCR method. Deletion of Ssr1 results in growth retardation at pH values ranging from 5.0 to 7.0 (P < 0.05), and the survival rate was reduced by 22% in acidic conditions (pH 3.0). Additionally, virulence was significantly increased in an Ssr1 mutant strain, as revealed in a murine lung invasion model and survival model assays. By using the sTarPicker method and proteomic analysis, we considered that DnaK, which is a major factor that confers acidic stress tolerance, may be a direct target of Ssr1. We also found that Ssr1 may enhance virulence by directly targeting OmpA; this leads to altered expression of genes in the type three secretion system (T3SS). This work provides new insight into the mechanism of adaptation to environmental stress and into the pathogenesis of Shigella.
福氏志贺菌是发展中国家细菌性痢疾的一个重要病因。小调控RNA（sRNA）在多种细胞过程中发挥着重要作用。我们通过逆转录聚合酶链反应（RT-PCR）、Northern印迹和5'端快速扩增cDNA末端（5'RACE）在福氏志贺菌中发现了一种新型sRNA Ssr1。使用定量逆转录聚合酶链反应（qRT-PCR）方法显示，Ssr1对酸性环境变化有反应，pH值与Ssr1表达之间存在很强的线性相关性（R = 0.785，P < 0.05）。缺失Ssr1会导致在pH值为5.0至7.0范围内生长迟缓（P < 0.05），在酸性条件（pH 3.0）下存活率降低22%。此外，在小鼠肺侵袭模型和存活模型试验中发现，Ssr1突变株的毒力显著增加。通过使用sTarPicker方法和蛋白质组学分析，我们认为赋予酸性应激耐受性的主要因素DnaK可能是Ssr1的直接靶点。我们还发现Ssr1可能通过直接靶向OmpA来增强毒力；这导致三型分泌系统（T3SS）中基因表达的改变。这项工作为福氏志贺菌适应环境应激的机制和发病机制提供了新的见解。
