中文摘要：

【目的】研究信号分子AI-2对禽致病性大肠杆菌（APEC）的调控作用。【方法】采用改良结晶紫半定量法和荧光染色法检测Al-2对APEC生物被膜形成能力的影响。Real-time PCR检测AI-2对APEC毒力基因转录水平的影响。活菌计数法观察Al-2对APEC黏附和入侵鸡胚成纤维细胞DF-1的影响。【结果】Al-2在浓度为0.185 mmol·L^-1时，生物被膜形成能力显著增强，而浓度为0.037mmol·L^-1和0.285mmol·L^-1时，生物被膜形成能力无显著变化。Real-time PCR结果显示加入AI-2后，APEC毒力基因pfs，vat，luxS，tsh，fuyA，iucD转录水平显著下调，ompA和iss则上调。加入AI-2后，APEC对DF-1细胞的黏附和入侵能力分别下降到原来的57.35%和36.64%。【结论】Al-2对禽致病性大肠杆菌生物被膜形成具有浓度依赖性，在适宜浓度下能显著增强。AI-2能减弱禽致病性大肠杆菌毒力基因的转录水平和对DF-1的黏附和入侵能力。表明AI-2参与调控APEC致病性。

英文摘要：

【Objective】 The aim of the study was to investigate the modulation of AI-2 on the biofilm forming ability and virulence in Avian Pathogenic Escherichia coli （APEC）. 【Method】 The improved crystal violet seme-quantitative method and fluorescence staining method were used to study the effects of AI-2 on the biofilm forming ability in APEC. The effects of AI-2 on the mRNA levels of the virulence genes were analyzed using real-time PCR. Viable bacteria counting method was used to evaluate the effects of AI-2 on the capability of APEC to adhere and invade DF-1cell. 【Result】The results showed that the biofilm forming ability decreased at the concentration of 0.185 mmol·L^-1 AI-2,while the biofilm forming ability had no significant change at the concentration of 0.037mmol·L^-1 and 0.278 mmol·L^-1 AI-2. Real-time PCR showed that Al-2 decreased the transcription of pfs, vat, lux, tsh, fuyA, iucD genes, while increased the transcription of ompA and iss genes. The adherence and invasion was decreased to 57.35% and 36.64% by supplementation with AI-2 in APEC. 【Conclusion】The biofilm forming ability increased at an optimal concentration of AI-2. The transcription of the virulence genes, the adherence and invasion to DF-1 cells of the bacteria were decreased by supplementation with AI-2 in the medium to culture the APEC. These findings will be of benefit to future studies of the role of AI-2 in APEC.