Research Article

The effect of ultrasound exposure on the transformation efficiency of Escherichia coli HB101

Kimran Hayer

University of Derby, Kedleston Road, Derby, DE22 1GB, UK


14 Sept 2009


6 Apr 2010


31 May 2010






Escherichia coli HB101, transformation, ultrasound, calcium chloride, transformation efficiency


Transformation is an important tool in modern genetic engineering and artificial methods exist to induce transformation in bacteria. Ultrasound offers the potential advantage of being versatile and less dependent on cell types than traditional methods like electroporation. This study investigated the effect of low-frequency ultrasound exposure on the ability of Escherichia coli (E. coli) to undergo transformation. E. coli HB101 in the presence of pBR322 plasmid was exposed to ultrasound frequencies of 48 kHz for 10–1200 s and monitored over a 24 and 48 h period. The most effective transformation efficiency (148.72 transformants µg−1 of DNA) was observed at 10 s exposure to ultrasound and after 24 h incubation. The ultrasound method was compared with the calcium chloride (CaCl2) method of inducing artificial competence. There was a significant difference between 0.05 mM CaCl2 induced transformation (4.70 transformants µg−1 of DNA) and 10 s exposure to ultrasound transformation (148.72 transformants µg−1 of DNA) after 24 h incubation. This study highlights the potential of ultrasound as a realistic alternative to induce competence for the genetic manipulation of bacteria.