Study on the Factors Affecting Transformation Ability of Competent Escherichia coli Cells

Several factors including Escherichia coli growth status,transformation solutions,freezing stabilizers and storage duration were evaluated for their effects on the transformation ability of competent Escherichia coli cells.The results suggested that the highest transformation ability can be obtained when Escherichia coli JM109 was cultured to an A600 of 0.56,prepared with 100 mmol/L CaCl2,and kept on ice for 6 h before transformation.As a stabilizer for frozen competent cells,the temperature of liquid nitrogen better than other three temperature.20% glycerol was found to be better than 10% DMSO,however,both of them inhibited transformation.