State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, Hohhot, China.
State Key Laboratory of Reproductive Regulation and Breeding of Grassland Livestock, School of Life Sciences, Inner Mongolia University, Hohhot, China; Department of Neurology, Inner Mongolia People's Hospital, Hohhot, China.
Gene. 2022 May 5;821:146295. doi: 10.1016/j.gene.2022.146295. Epub 2022 Feb 15.
Response to acid stress is critical for Escherichia coli to successfully complete its life-cycle. Acid resistance is an indispensable mechanism that allows neutralophilic bacteria, such as E. coli, to survive in the gastrointestinal tract. Escherichia coli acid tolerance has been extensively studied over the past decades, and most studies have focused on mechanisms of gene regulation. Bacterial two-component signal transduction systems sense and respond to external environmental changes through regulating genes expression. However, there has been little research on the mechanism of the TorR/TorS system in acid resistance, and how TorR/TorS regulate the expression ofacid-resistantgenes is still unclear. We found that TorR/TorS deletion in E. coli cells led to a growth defect in extreme acid conditions,andthis defectmightdepend on the nutritional conditionsand growth phase.TorS/TorR sensed an extremely acidic environment, and this TorR phosphorylation process might not be entirely dependent on TorS.RNA-seqand RT-qPCR results suggested that TorR regulated expressions of gadB, gadC, hdeA, gadE, mdtE, mdtF, gadX, and slp acid-resistant genes. Compared with wild-type cells, the stress response factor RpoSlevels and itsexpressions were significantly decreased in Δ torR cellsstimulated by extreme acid. And under these circumstances, the expression of iraM was significantly reduced to 0.6-fold inΔ torR cells. Electrophoreticmobility shift assay showed that TorR-His could interact with the rpoS promoter sequence in vitro. β-galactosidase activity assayresultsapprovedthat TorR might bind the rpoS promoter region in vivo. After the mutation of the TorR-box in the rpoS promoter region, these interactions were no longer observed. Taken together, we propose thatTorS and potential Hanks model Ser/Thr kinase received an external acid stress signal and then phosphorylated TorR, which guided the expressions of a variety of acid resistance genes. Moreover,TorRcoped with extreme acid environmentsthroughRpoS, levels of which might be maintained byIraM. Finally,TorR may confer E. coli with the abilityto resist gastric acid, allowing the bacterium to reach the surface of the terminal ileum and large intestine mucosal epithelial cells through the gastric acid barrier, andestablishcolonization and pathogenicity.
响应酸应激对于大肠杆菌成功完成其生命周期至关重要。抗酸性是一种必不可少的机制，使嗜中性细菌（如大肠杆菌）能够在胃肠道中存活。几十年来，人们对大肠杆菌的酸耐受性进行了广泛的研究，大多数研究都集中在基因调控机制上。细菌双组分信号转导系统通过调节基因表达来感知和响应外部环境变化。然而，关于 TorR/TorS 系统在酸抗性中的作用机制的研究甚少，并且 TorR/TorS 如何调节酸抗性基因的表达仍然不清楚。我们发现，大肠杆菌细胞中 TorR/TorS 的缺失导致其在极端酸性条件下的生长缺陷，而这种缺陷可能取决于营养条件和生长阶段。TorS/TorR 感知到极度酸性的环境，而 TorR 的磷酸化过程可能不完全依赖于 TorS。RNA-seq 和 RT-qPCR 结果表明，TorR 调节 gadB、gadC、hdeA、gadE、mdtE、mdtF、gadX 和 slp 等酸抗性基因的表达。与野生型细胞相比，在受到极端酸性刺激时，Δ torR 细胞中的应激反应因子 RpoS 水平及其表达显著降低。在这些情况下，Δ torR 细胞中 iraM 的表达显著降低至 0.6 倍。电泳迁移率变动分析显示，TorR-His 可以在体外与 rpoS 启动子序列相互作用。β-半乳糖苷酶活性测定结果证实，TorR 可能在体内结合 rpoS 启动子区域。当 rpoS 启动子区域中的 TorR 盒发生突变时，这些相互作用不再观察到。综上所述，我们提出 TorS 和潜在的 Hanks 模型 Ser/Thr 激酶接收外部酸应激信号，然后磷酸化 TorR，指导各种酸抗性基因的表达。此外，TorR 通过 RpoS 应对极端酸性环境，而 IraM 可能维持 RpoS 的水平。最后，TorR 可能赋予大肠杆菌抵抗胃酸的能力，使细菌通过胃酸屏障到达回肠末端和大肠黏膜上皮细胞，并建立定植和致病性。
