一种新的质粒克隆载体的稳定性和拷贝数的测定

Stability and copy number in host bacteria of a new plasmid cloning vector

为了研究Ｃｏ１Ｅ２质粒的复制及其调控机理，构建了一种新的质粒克隆载体ｐＢｌｕｅｓｃｒｉｐｔ２２＋，并且测定了它在宿主中的稳定性和拷贝数。结果表明，在宿主菌繁殖４０代前，它在宿主菌中的拷贝数达到最高，之后便很快下降，虽然在宿主菌繁殖到１８０代时它仍未从所有宿主菌中完全丢失；而且，加入氯霉素可以提高它在宿主中的拷贝数。这提示，为了获得更多的质粒，应在宿主菌培养４０代前并在向培养液中加入氯霉素继续培养２ｈ内收获质粒。

A new plasmid cloning vector pBluescript22 + was constructed to study the mechanism of the replication and its regulation of plasmid CoIE2. Its stability and copy number in host bacteria were mea-sured . The results showed that it reached its highest copy number before its host bacteria grew to 40 gener-ations although it could still maintain in host bacteria until 180 generations. This suggests that plasmid should be drawn out before the host bacteria grow to 40 generations, accompanied by the addition of chlo-ramphenicol ,in order to harvest more plasmids.