群体感应系统受体SdiA对大肠杆菌生物学 特性的影响

Effects of quorum sensing system receptor SdiA on biological characteristics of Escherichia coli

群体感应系统能够使大肠杆菌(Escherichia coli)感知并适应环境的应激压力,对其生物被膜形成、抗逆性具有重要意义。SdiA是Ⅰ型群体感应系统的受体蛋白,能够识别信号分子并调控下游基因,提高大肠杆菌的抗胁迫能力。本文以大肠杆菌工程菌株BL21(DE3)为研究对象,通过异源表达Ⅰ型群体感应系统受体蛋白SdiA,考察SdiA对细菌生物被膜形成、运动性和抗逆性等生物学特性的影响。结果表明,重组菌株E.coli BL21(DE3)pET28a sdiA的生物被膜产量较野生株显著降低了20.03%。同时,大肠杆菌中表达的受体蛋白SdiA能够对信号分子C4 HSL完成应答,并进一步抑制生物被膜形成。培养24 h后,SdiA表达菌株的运动半径相较于野生株降低了62.5%。在酸性环境中(pH=3),SdiA表达株的细菌存活率提升了9.27倍;在高渗透压环境中,SdiA表达株的细菌存活率较野生株提升了62.76%。荧光定量PCR结果显示,aphA基因在SdiA表达株中表达量上调了41.76%;lsrB基因的表达量降低30.47%;鞭毛和菌毛形成相关基因motB、csgD、fimA和fimC的表达水平分别下调了48.39%、39.57%、49.67%和23.21%。以上结果表明,SdiA蛋白通过调控群体感应以及运动性相关基因的转录,进而抑制大肠杆菌生物被膜形成和泳动性。同时,SdiA蛋白作为大肠杆菌中重要的转录因子,在其遭遇酸性条件和渗透压胁迫时具有正向调控作用。因此,本文揭示了SdiA蛋白对大肠杆菌工程菌株生物学特性的调控作用,为利用群体感应精准调控菌群行为提供了有效靶点。

The quorum sensor system could improve the ability of Escherichia coli to perceive and adapt to environmental stress,a highly important factor for biofilm formation and stress resistance.SdiA,the receptor protein of type I quorum sensing system in Escherichia coli,can recognize signal molecules and improve stress resistance.Herein,we studied the receptor protein SdiA,which was expressed in E.coli BL21(DE3),with regards to its effects on the biological characteristics of bacterial biofilm formation,motility and stress resistance.As a result,the E.coli BL21(DE3)-pET28a-sdi A could significantly reduce the biofilm formation by 20.03%compared with the wild-type strain.Moreover,the receptor protein SdiA in E.coli could respond to the signalling molecule C4-HSL and further inhibit biofilm formation.After culturing for 24 h,the movement radius of the SdiA-expressing strain decreased by 62.5%compared with that of the wild-type strain.In an acidic environment(pH=3),the survival rate of the SdiA-expressing strain increased by 9.27 times.In a high osmotic pressure environment,the survival rate of the SdiA-expressing strain increased by 62.76%.According to the qPCR results,the RNA expression of aph A gene in the SdiA-expressing strain increased by 41.76%,while 30.47%decrease was observed for lsr B gene.The expression levels of genes related to flagella and fimbriae formation,such as mot B,csg D,fim A and fim A,decreased by 48.39%,39.57%,49.67%and 23.21%,respectively.The above results demonstrated that SdiA protein could inhibit biofilm formation and motility of E.coli by regulating quorum sensing and the transcription of sports-related genes.Meanwhile,SdiA protein acted as an important transcription factor in E.coli,leading to a positive regulatory effect under acidic conditions and osmotic pressure.Overall,SdiA protein was thoroughly studied with regards to its regulatory effects on the biological characteristics of engineered E.coli strains,suggesting its potential to be an effective target in accurately regulating the behavior of flora through quorum sensing.