Transformation of commercial baker's yeast strains by electroporation

We developed an electroporation protocol for transformation which was particularly optimized for commercial baker's yeast strain. The protocol is based on the standard Biorad Gene Pulser/Pulse Controller machine. It works efficiently both for the introduction of standard multicopy plasmids (ARS and 2 mu m based) and for integrative transformation. In particular we were able to transform genuine prototrophic baker's yeast strains with a 2 mu m-based multicopy plasmid, carrying the dominant sulfometuron methyl resistance marker. For plasmids requiring the introduction of more than one copy for complementation, the transformation frequency was considerably lower. This suggests that transformation by the electroporation method introduces on average only one or a few copies of the transforming plasmid per cell.