High efficiency transformation of intact yeast cells by electric field pulses

We have developed an efficient method that electrically introduces DNA into intact yeast cells. Saccharomyces cerevisiae was used as a model in order to optimize the transformation protocol. Transformation efficiencies of 10(7) transformants/micrograms of plasmid DNA were obtained with a square wave electric pulse of 2.7 kV/cm during 15 milliseconds. The technique is simple and rapid. Even small quantities of DNA (100 pg) can be used to transform 10(8) cells. Important parameters are the pulse field strength and duration. Pretreatment of the yeast cells in the early phase of exponential growth with dithiothreitol increases transformation efficiency. The method has been successfully applied to various strains of S. cerevisiae as well as to other types of yeast.