猪链球菌荚膜多糖合成相关基因簇保守区的克隆与分析

Cloning and analysis of the conserved regions in the capsular polysaccharides synthesis locus of Streptococcus suis

【目的】为了解猪链球菌各血清型荚膜多糖合成相关基因保守区的功能与基因进化关系,【方法】在分析已知的猪链球菌1、2、7、9型荚膜多糖合成相关基因簇序列,及其各orf与猪链球菌33个血清型基因组DNA杂交结果的基础上,提出猪链球菌荚膜多糖合成相关基因簇具有与肺炎链球菌相似的盒样结构的假设。并采用PCR、测序和Southern印迹杂交等方法验证这些假设。【结果】结果显示,猪链球菌的荚膜多糖合成相关基因簇确存在与肺炎链球菌相似的盒样结构,5'端的前4个调节相关基因同源性极高,基因簇两端都有保守的侧翼基因,且在3'端的侧翼序列中找到了适于扩增荚膜多糖合成相关基因簇中血清型特异性区域的下游引物所在基因(aroA)。分析发现,各血清型的orfY、orfX、cpsA、cpsB、cpsC、cpsD和aroA的亲缘关系较近。

[Objective] To learn about the function and gene phylogenetic relationship of the conserved regions in capsular polysaccharides synthesis（CPS） locus,[Methods] based on the CPS locus sequence of Streptococcus suis serotype 1,2,7 and 9 and the results to the cross-hybridization experiments,the CPS locus of Streptococcus suis was hypothesized as cassette-like structure which is similar to Streptococcus pneumoniae.PCR,sequencing and southern blotting was used to certify the hypothesis.[Results] The CPS locus of Streptococcus suis was cassette-like structure.The 5′-end of the CPS locus contained 4 regulatory genes which are highly similar in all the serotypes.The flanking genes of the CPS locus are conservative.The flanking gene aroA,which is at the downstream to the CPS locus,was selected as the objective gene to develop the PCR to amplify the serotype-specific regions.The orfY、orfX、cpsA、cpsB、cpsC、cpsD and aroA are conserved with high sequence identity in different serotypes.