荚膜异多糖酸合成调节子(regulator of colanic acid capsule synthesis，Rcs)对大肠埃希菌适应外环境压力具有重要调控功能，但其在志贺菌中的功能尚未见报道。为探索外环境压力对福氏志贺菌Rcs编码基因rcs转录水平的影响，本研究采用核苷酸序列比对及蛋白结构域预测等生物信息学方法分析福氏志贺菌的Rcs编码基因簇rcsBDC，利用实时定量聚合酶链反应(quantitative real-time polymerase chain reaction，qRT-PCR)，对该菌不同生长时期的rcsB、rcsD、rcsC基因转录水平进行分析，并检测在不同pH值培养基、渗透压条件下的基因转录水平。结果显示，福氏志贺菌rcsBDC在培养5～6 h(对数中期)时转录水平较高，8～10 h(稳定期)时转录水平较低(P<0.001)；10 h时，rcsB和rcsD在酸性、渗透压条件下的转录水平均显著高于正常条件下的转录水平(P<0.05)。结果提示，外环境刺激可提高福氏志贺菌在稳定期的rcsB和rcsD转录水平，为志贺菌适应胃肠道酸性、渗透压环境的机制研究提供了一定理论基础。

The regulator of colanic acid capsule synthesis (Rcs) is a complicated two-component signal transduction system. Although details of Rcs in most Enterobacteria are known, its regulation in Shigella has not been reported yet. This study aims to explore the influences of environmental stresses on Rcs transcription in Shigella. Based on biological informatics analysis of RcsBDC in Shigella flexneri 2a 301, the transcriptional levels of rcsB, rcsD, rcsC at different growth stages were analyzed by real-time polymerase chain reaction (PCR), and the changes in the transcriptional levels of the three genes in acid and osmotic pressure conditions were examined. The transcriptional levels of the three genes were higher in 5－6 h (logarithmic phase), and lower in 8－10 h (stationary phase). The transcriptional levels of rcsB and rcsD in acid and osmotic pressure conditions were higher than in normal condition, suggesting environmental stimuli promote the transcriptional levels of rcsB and rcsD in Shigella flexneri during stationary phase.