Microwave improved Escherichia coli transformation

• Published in: Letters in applied microbiology Vol. 46; no. 4; pp. 498 - 499
• Main Authors: Fregel, R, Rodríguez, V, Cabrera, V.M
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.04.2008; Blackwell Publishing Ltd; Blackwell Science
• Subjects: Biological and medical sciences; cloning; Escherichia coli; Escherichia coli - radiation effects; Fundamental and applied biological sciences. Psychology; Genetics, Microbial - methods; Microbiology; microwave; Microwaves; plasmid DNA; transformation; Transformation, Bacterial - radiation effects; Plasmid; plasmid DNA; Applied microbiology; DNA; Escherichia coli; Microwave; Bacteria; Eschenchia coli; transformation; cloning; Enterobacteriaceae
• ISSN: 0266-8254; 1472-765X
• DOI: 10.1111/j.1472-765X.2008.02333.x

The calcium chloride chemical transformation of Escherichia coli is still the most widley used cloning method in small laboratories. Therefore, any practicable improvement in its transformation efficiency seems to be of general interest. We found that giving calcium chloride competent cells a 1 min microwave pulse at the lowest power setting (180 W), instead of the classic 1-2 min 42°C heat-shock step, increases the transformation efficiency around threefold (3.3 ± 0.5). Moreover, when both treatments were given in a 2-min 42°C - 5 min on ice - 1 min microwave pluse sequence, an additional improvement of 1.6 was obtained, resulting in an overall increase in efficiency of approximately 5.3-fold compared to classical heat shock. This transformation method significantly improves the classical heat shock treatment. This method might be useful to those laboratories that cannot afford an electroporation apparatus.