phoP/Q双组分系统对禽致病性大肠杆菌的毒力调控作用

The Role of phoP/Q Two-component System in Virulence of Avian Pathogenic Escherichia coli

phoP/Q作为一种外在环境感受器,参与调节细菌对外部环境的适应性。本研究拟探讨phoP/Q双组分系统对禽致病性大肠杆菌(APEC)的生长、定植、毒力等生物学特性的影响。利用Red重组系统构建APEC AE 17株的phoP/Q双组分调控系统缺失株,并构建phoP/Q双组分调控系统回复质粒,转化缺失株,构建回复株。通过生长运动性试验、黏附入侵CEF细胞试验、毒力基因转录水平检测以及半数致死量(LD50)等试验比较野生株、缺失株、回复株的生物特性。与野生株相比,phoP-phoQ缺失不改变其生长特性;运动性较野生株下降63%;黏附与入侵CEF细胞能力分别降低69.83%(P<0.01)和62.17%(P<0.05);LD50显示毒力减弱13.3倍;polA、tsh基因转录水平分别上调41%、54%;sodA、iss分别下调64%和98%。phoP/Q双组分系统参与对APEC致病性的调控,该系统的缺失会降低APEC的致病性。

As a kind of external environment receptor,phoP/phoQ is involved in regulating bacterial adaptability to external environment.The aim of this study was to investigate the effect of phoP/Q two-component system to biological characteristics of avian pathogenic Escherichia coli（APEC）such as growth,engraftment,and virulence.The phoP-phoQ deletion mutant strain was constructed by homologous recombination assay,and the complement strain was constructed through transformation deletion strain with the plasmid complement.The growth curve determination and motility assay,the adhesion and invasion to chicken embryo fibroblast（CEF）,detection of virulence gene transcription and median lethal dose（LD50）experimental were used to compare biological characteristics of wild strain,deletion strain and complement strain.Compared with the wild strain,the growth characteristics of the mutant strain did not change;the motility of the mutant strain felled by 63% comparing with wild strain;its ability of adhesion and invasion to DEF cells respectively decreased to 69.83% and 62.17%;and LD50 was significantly reduced by13.3times.The transcription of polA,tshrespectively increased by 41%and 54%,while the sodA and iss decreased by 64%and 98%.The phoP/Q two-component system is involved in the regulation of the APEC pathogenic,and its deletion can reduce the pathogenicity of APEC.