中文摘要：

为探明内蒙古的8株嗜热链球菌的CRISPR，用PCR方法扩增了其CRISPR序列，并采用生物信息学方法分析和预测了重复序ylJ（directrepeat，DR）的同源性及二级结构。结果表明：除S4只含有一个CRISPR结构外，其余7株嗜热链球菌均检测出3条CRISPR序列，远高于CRISPRdatabase公布细菌中具有该结构的比例（46．4％），且分别具特异性的重复序列（DR1-DR3）；CRISPR最长达2853bp，最短仅101bp。对DR的二级结构预测发现，DRl～DR3均能形成回文结构，但茎环大小会有差异；在同源性比对中发现，除多数同属或同种外，供试DR还与个别远缘菌种具有高同源性，这种现象证明了供试菌株的CRISPR序列同样存在的水平基因转移，并可能存在其他的进化进程。

英文摘要：

CRISPR was recently found to be an acquired immune system widespread in prokaryotes. In order to find out CRISPRs in 8 Streptococcus thermophilus strains isolated from Inner Mongolia, the CRISPR sequences were obtained by PCR amplification, and homology and secondary structure of direct repeat （DR） were predicted using bioinformatic methods. Results showed that all studied strains contained three CRISPR sequences except one in $4, which was much higher than the ratio （46.4%） in bacteria published on CRISPR database, and three CRISPRs had their specialized direct repeats （DR1--DR3）. The longest CRISPR was 2853 bp, and the shortest was only 101 bp. According to the prediction of secondary structure, a palindrome was detected in DR1--DR3, respectively, although the sizes of stem-loops were different. For homology analysis, DR demonstrated high similarity with several individual species of distant relationships like those in the same genus or species, which suggested that the CRISPRs of tested strains also had the characteristic of horizontal gene transfer （HGT）, as well as the possibility of other evolutionary process.