PLASMID PSL2 AND ITS PREPARATION

摘要

PURPOSE:To prepare a large amount of plasmid pSL2, by obtaining a double- chain cyclic plasmid having desirable properties as a vector from Streptococcus lactic No.128. CONSTITUTION:Plasmid pSL2 which is a double-chain cyclic DNA having a molecular weight of 4.4X10<6> Dalton and containing ampicillin-resistant gene and tetracycline-resistant gene in the molecule is prepared beforehand. The plasmid pSL2 is cloned to Escherichia coli, and the bacteria are cultured in the presence of chloramphenicol to increase the content of the plasmid pSL2 in the cell.