Effects of Freezing Time During Preparation of Competent Cells and Plasmid Transformation on Transformation Efficiency of E.coli

The affecting factors on transformation efficiency of E.coli were studied,which include plasmid DNA dosage putting into transforming system,freezing time during preparation of competent cells and plasmid transformation.These tests were used to analyse the best transforming parameters and optimize the methods of preparation of competent cells and plasmid transformation.The results indicated that the parameters of the highest transformation efficiency in this study were 1～10 ng of plasmid(pBR322) DNA dosage,30～60 min of freezing time during preparation of competent cells,as well as 30 min and 120 min of freezing time during plasmid transformation.Out of these conditions,it decreased the transformation efficiency of E.coli.The results of this study will provide technology basis for the transformation tests requiring high transformation efficiency.