Speaker
Description
Bacterial transformation is the internalization of exogenous DNA and integration into the recipient genome via homologous recombination, which can result in bacteria acquiring possible new genetic traits. The laboratory standards for bacterial transformation requires chemically competent cells and despite the reported high efficiencies, chemical and heat shock transformation methods have limited success in wild-type and pathogenic bacterial strains. As an alternative, electroporation is commonly used as it allows for the uptake of large amounts of genetic material, e.g., plasmids, and bacterial artificial chromosomes (BACs in the range of 150−350 kb). Nevertheless, electroporation can lead to cell death, primarily when the electric fields cause permanent membrane permeabilization. Here, we report a novel method of genetic transformation of bacterial cells mediated by high-frequency microwave radiation. Escherichia coli JM109 was exposed to a frequency of 18 GHz at a power density between 5.6 and 30 kW m−2 for 180 s, using a specialised microwave processing apparatus that limited the temperature rise to below 40 °C. Plasmid DNA, pGLO (5.4 kb), was successfully transformed into E. coli cells as evidenced by the expression of green fluorescent protein (GFP) using confocal scanning microscopy and flow cytometry. Approximately 90.7% of the treated viable E. coli cells exhibited uptake of the pGLO plasmid. The interaction of plasmid DNA with bacteria leading to transformation was further confirmed using cryogenic transmission electron microscopy.
