质料拷贝数对宋内氏菌I相O—抗原表达的影响

试图通过提高质粒拷贝数来提高宋内Ｉ相Ｏ－抗原的表达水平，先将宋内Ｉ相Ｏ－抗原基因亚克隆至高拷贝的ｐＵＣ１８和ｐＧＥＭ３Ｚ，但没能找到相应的阳性转化子，可能Ｏ－抗原基因在高拷贝质粒上表达水平太高对宿主产生毒性效应。再将其亚克隆至中等拷贝的ｐＡＴ１５３，虽能找到阳性转化子，但表达水平仍不能满足以后实验的需要，表明质粒拷贝数与Ｉ相Ｏ－抗原的表达水平密切相关，要有效地表达宋内Ｉ相Ｏ－抗原，还需要寻找拷贝数

Influence of plasmid copies on the expression of Shigella sonnei form I O-antigen

In this research the expression level of S.sonnei form I O-antigen was tried to raise by increasing copies of plasmids. Firstly S.sonnei form I O-antigen gene was subcloned into high-copy plasmids pUC18 and pGEM3Z, but no positive transformants were found. It is possible that the epression level of from I O-antigen is so high that it is toxic to host strain. Then form I O-antigen gene was subcloned into pAT153 with medium copies. Though the positive transformants were got, their expression level was not high enough to induce effective specific immunoreaction. These data showed that the expression level of form I O-antigen was closly related to copies of plasmids. In order to obtain an effective expression of form I O-antigen, it is necessary to find a plasmid with more suitable copies.