猪链球菌9型cps9G基因的克隆与序列分析

Cloning and Sequence Analysis of cps9G Gene of Streptococcus suis Serotype 9

根据GenBank中猪链球菌9型（SS9）基因的核酸序列，设计一对引物，采用PCR方法从确诊为猪链球菌的阳性样品中扩增cps9G基因片段，将其克隆到pMD18-T载体上，转化DH5a感受态细胞，提取重组质粒pMD18T-cps9G，经PCR和酶切鉴定后测序，并与GenBank上SS9相应序列进行同源性分析。结果表明，经PCR扩增，鉴定为SS9的有8株。序列分析发现，8株SS9的cps9G片段的核苷酸序列较稳定，该基因片段长度均为562bp，彼此间的核苷酸同源性达96．8％～99．8％，亲缘关系密切；与GenBank上已发表的SS9参考毒株的同源性介于96．0％～98．6％。

A pair of specific primers were designed according to the sequence of Streptococcus suis serotype 9 gene in GenBank. The cps9G gene was amplified from the final diagnosed Streptococcus suis samples by PCR, the amplified fragments were cloned into the pMD18-T vectors, and the positive recombinant plasraids were sequenced. The results showed that, eight SS9 were isolated, the complete genome of every strain consisted of 562 bp. Nucleotide sequence homologies between the eight SS9 isolates were found to be 96.8%-99.8%. The homologies were 96.0%-98.6% compared with the sequences of SS9 in GenBank.