中文摘要：

目的获得牛乳腺炎无乳链球菌分离菌株pgk基因序列,分析其基因与氨基酸的同源性。方法参考Gen-Bank上公布的牛源无乳链球菌pgk基因序列设计合成1对引物,通过PCR扩增获得其序列并进行克隆与测序分析。结果所扩增的pgk基因序列的大小为1 197 bp,负责编码399个氨基酸残基。对比扩增的分离菌株pgk基因序列与GenBank上公布的B群无乳链球菌pgk基因（AE009948）相似性达到99.83%,编码的氨基酸序列相似性达到99.74%。结论该基因序列具有高度的保守性,为进一步对分离菌株的pgk基因进行高效表达及其产物的抗原性研究奠定了基础。

英文摘要：

Objective To obtain the pgk gene sequences of an isolated strain ofStreptococcus agalactiaecausing bovine mastitis and analyze the homology of the gene and amino acids.Methods A pair of primers was designed and synthesized according to pgk gene sequences ofS.agalactiaepublished on GenBank.The gene sequences was amplified by PCR and then cloned and analyzed.Results The amplified pgk gene was 1 197 bp in length and encoded 399 amino acid residues.The amplified pgk gene from the isolated strain and the pgk gene from a group B strain ofS.agalactiae（AE009948） published on GenBank had a homology of 99.83% and a homology of coded amino acids of 99.74%.Conclusion Gene sequences were highly conserved and laid the grounds for further study of high expression of the pgk gene from an isolated strain ofS.agalactiaeand the antigenicity of the expression products.