中文摘要：

目的筛选出能特异性识别大肠埃希菌O157：H7的单链DNA（ss DNA）适配体并进行鉴定。方法利用全菌消减SELEX技术,以完整菌体为靶标菌和消减菌,通过体外筛选方法筛选出大肠埃希菌O157：H7特异性ss DNA适配体。利用荧光分光光度计、激光共聚焦显微镜、克隆测序、Chromas和DNAMAN分析软件,分析适配体的一、二级结构,并对筛选得到的适配体进行特异性鉴定。结果经过7轮全菌消减SELEX筛选,荧光分光光度计检测结果鉴定第六轮文库富集达到饱和;通过测序分析、荧光分光光度计和激光共聚焦显微镜特异性检测,获得1条与大肠埃希菌O157：H7特异性结合的适配体Aptamer1。结论利用全菌消减SELEX技术成功筛选获得大肠埃希菌O157：H7特异性ss DNA适配体。

英文摘要：

Objective To select and identify ss DNA aptamers which can specifically bind to the Escherichia coli O157：H7.Methods With whole bacteria as target and counter target, whole-bacterium based subtractive SELEX was used to screen the Escherichia coli O157：H7-specific ss DNA aptamer. The selection procedure and aptamer was identified by spectrophotofluorometer, confocal laser scanning microscope,gene cloning and sequencing; Chromas and DNAMAN software were employed to analyze the primary structure and predict the secondary structure of the aptamer. Results After seven selection rounds, the identification of spectrophotofluorometer showed the enrichment of ss DNA in the sixth round had reached saturation. The Escherichia coli O157：H7-specific aptamer named Aptamer 1 was eventually singled out after gene sequencing and specificity test by spectrophotofluorometer and confocal laser scanning microscope. Conclusion The Escherichia coli O157：H7-specific aptamer has been successfully obtained after seven round selection by whole-bacterium based subtractive SELEX.