含par位点的重组质粒Psjm3的构建及其稳定性研究

利用自然质粒pSC101par位点的分离稳定性功能，构建了含par位点的质粒pSJM4和pSJM3，通过在同样宿主E.coli HB101中的稳定性比较研究表明，不含par位点的重组质粒pSJ3很不稳定，E.coli G3(pSJ3)在培养到第10代时已开始出现pSJ3的丢失，到培养至50代时则已全部丢失；而含par位点的重组质粒pSJM3则表现得十分稳定，E.coli G3-1(pSJM3)经70代培养，仍无明显的质粒丢失现象，其稳定率保持97%以上。通过对不含par和含par的非重组质粒pUC18和pSJM4的稳定性比较也获得同样的结果。通过对E.coliG3(pSJ3)和E.coli G3-1(pSJM3)的产酶活性比较研究表明，G3-1菌株明显高于G3菌株，说明我们构建的重组质粒pSJM3上的par位点功能不仅没有因外源基因的表达而受影响，而且有利于外源基因的表达。

Construction of Recombinant Plasmid pSJM3 Containing par Region and Study on Its Stability

The plasmids pSJM4 and pSJM3,which contain both par region,were constructed.The comparative studies on stabilities of plasmids in same host ( E.coli HB101) showed that recombinant plasmid pSJ3 containing 2 8kb alkakine protease gente fragment but not par region was very instable.Some of G3(pSJ3) strains lost their plasmids when they were cultured to 10 generations in nonselected medium,and no plasmids,essentially,were detected to 50 generations.However,the recombinant plasmid pSJM3 which consists of pSJ3 and par region was extremly stable.When G3 1(pSJM3) strain was cultured even to 70 generations,no plasmids were almost lost from their host populations,and rate of stability is over 97%.Same result was obtained by comparative studies on stabilities between pUC18(par) and pSJM4 (par ) The comparison of activities of alkaline protease produced by strains G3 (pSJ3) and G3 1(pSJM3) indicated that the enzyme activity produced by strain G3 1(pSJM3) was higher than that of strain G3 (pSJ3).It is proved that function of par region inserted in pSJM3 not only is unaffected by expression of foreign genes but is favourable