Designing Novel Method for Increasing the External DNA Transformation Efficiency into the Escherichia coli, based on a Membrane Permeable Peptide

Aim and High efficient transformation of external DNA into the bacterial cells accounts as the main step of microbial biotechnology. For this purpose, some conventional methods have been developed. Using cold CaCl2 is one of the most important and cheapest ways for DNA transformation into the gram negative bacteria such as Escherichia coli. Commonly used methods have a low transformation rate about 105 to 107 transformants per 1μg of DNA. Due to the importance of DNA transformation procedure, numerous attempts have been applied to optimize the conventional methods such as cold CaCl2. In this study we showed that it is possible to increase DNA transformation efficiency into the E. coli in standard CaCl2 method, using a membrane permeable cationic peptide (CM11). Based on ClCa2 competent cell preparation method, the bacterial cells were treated by different concentration of peptide (0.5, 1, 2, 3 and 6 μg/ml) in two different ways. Thereafter pET-28a (+), pGEX4T-1 and pUC19 as model plasmids were separately transformed into the competent cells. Results showed that the highest plasmid transformation efficiency obtained at the present of 1 μg/ml of peptide. In this concentration, the transformation efficiency of pET-28a (+), pGEX4T-1 and pUC19 plasmids were respectively 4.4, 4.7 and 4 fold higher than control sample. The results of this study revealed that in the chemical cold CaCl2 strategy for DNA transformation, CM11 as a cell membrane permeable peptide can increase the efficiency of DNA transformation into E. coli.