Vol.26 No.4£¨2004 August£©£º429-432 Factors Affecting Transformation Ability of Competent Escherichia coli Cells Lan-Lan Zhang, Chun-Yan Xu, Chang-Jie Xu* £¨Department of Horticulture; The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development & Biotechnology, Zhejiang University, Hangzhou 310029, China£© Abstract: A number of factors including strains, bacterium activation, growth status, transformation solutions, plasmid length and purity, freezing stabilizers and storage duration were evaluated for their effects on transformation ability of competent Escherichia coli cells. The results suggested that the highest transformation ability can be obtained when activated TG1 was cultured to an A600 of 0.55, prepared with 100 mmol/L CaCl2, and kept on ice for 6 h before transformation. When pUC19 was applied, the transformation efficiency for optimized protocol was found to be as high as between 2¡Á106-4¡Á107 cfu/mg DNA. The efficiency decreased when a plasmid with increased length or a plasmid sample with impurities was applied. As a stabilizer for frozen competent cells, 15% glycerol was found to be better than 7% DMSO, however, both of them inhibited transformation. Competent cells stored in glycerol retained desirable transformation efficiency for 2 months at -70 ¡æ. Key words: Escherichia coli; competent cells; transformation ability *Corresponding author. Tel: 86-571-85952426, Fax: 86-571-86049815, E-mail: chjxu@zju.edu.cn |