中文摘要：

为了制备高转化效率的E．coliTG1和E．coliDH5a感受态细胞，采用电转化方法探索E．coli生长对数期的不同生长阶段、质粒DNA含量、电场强度对E．coli转化效率的影响。研究结果表明：40μL菌液中加1．0ngpUC19DNA，用间隙0．2cm电击杯时转化效率最高，E．coli TG1有1个电转化效率峰值，即A600为0．665时，转化效率达1．7×10^9cfu／μg pUC19DNA；E．coliDH5a有2个转化效率峰值，即A600为0．443和0．810时，转化效率均为3．0×10^9 cfu／μg pUCl9DNA。研究结果表明，在相同情况下E．coliDH5a的转化效率高于E．coli TG1，利用本实验确定的参数可制备出高转化效率的电转化感受态细胞。

英文摘要：

To establish a high efficiency of electrotransformation , two different strains of E. coli DH5a and E. coli TG1 were used to investigate the influence of growth period during log phase, the content of the plasmid PUC19 DNA and the electric field strength on electrotransformation efficiencies. A highest electrotransformation efficiency was achieved at when 1.0 ng of plasmid DNA was used with 40μl solution and packed in 0.2 cm cuvette. A peak of electrotransformation efficiency for E. coli TG1 was 1. 7× 10^9 transformants per μg PUC19 DNA when the optical density （A600） was 0. 665 . Two peaks of electrotransformation efficiencies for E. coli DH5α were the same as 3.0×10^9 transformants per/tg PUC19 DNA when the optical density （A600） were 0. 443 and 0. 810. The results suggested that the transformation efficiency of E. coli DH5α was higher than E. coli TG1 with the identical condition and the parameters of the this experiment can be further applied to prepare the high efficient competent cell.