禽源和猪源大肠杆菌1型菌毛主要亚单位抗原多样性分子基础的初步研究

The Molecular Basis for the Antigenic Diversity of Type 1 Pili on Avian Escherichia coli

从禽源大肠杆菌037(O78)、166(O78)、120(O18)分离株和猪源大肠杆菌107/86分离株分别提取基因组DNA,并以此为聚合酶链反应(polymerasechainreaction,PCR)的模板,扩增上述分离株的1型菌毛主要亚单位结构基因pilA,得到了大小约570bp的扩增产物,将此扩增产物克隆于T载体,通过内切酶酶切分析得到4个阳性重组质粒;对上述4个大肠杆菌分离株的pilA基因进行序列测定,通过其编码的主要菌毛亚单位FimA蛋白氨基酸的序列比较发现:3个禽源株间FimA的同源性为94.3%至99.0%;禽源株和猪源株间FimA的同源性为89.6%至91.1%。在pilA开放性阅读框所编码的FimA182个氨基酸序列中,禽源大肠杆菌O78血清型的2个分离株037株和166株间只有2个氨基酸不同,其同源性为99.0%。

In order to determine the molecular basis for the antigenic diversity of type 1 pili on avian Escherichia coli, the genomic DNA samples of avian Escherichia coli isolates 037(O78), 166(O78), 120(O18) and porcine Escherichia coli isolate 107/86 were extracted respectively, and used as templates for polymerase chain reaction (PCR) to amplify the pilA gene encoding the major subunit protein of type 1 pili. The specific amplicons about 570bp in length were cloned into T vector, and 4 positive recombinant plasmids were obtained by RE digestion analysis.The nucleotide sequences of pilA genes from 4 Escherichia coli isolates were determined. By comparison, the homology of amino acid sequences of FimA proteins encoded by pilA of those isolates was 94.3% to 99.0% among 3 avian isolates, and 89.6% to 91.1% between avian isolate and porcine isolate. These results suggested that antigenic diversities of type 1 pili exist not only between avian Escherichia coli isolates and procine Escherichia coli isolate,but also exist between different avian Escherichia coli isolates beloneged to the same O serotype, e.g.isolate 037 O78 isolate and 166 O78.