A transformation system for the biocontrol yeast, Candida oleophila, based on hygromycin B resistance

Lithium acetate transformation and electroporation were applied to the biocontrol yeast, Candida oleophila. The hygromycin B resistance gene, flanked by the phosphoglycerate kinase promoter and terminator of Candida tropicalis, served as the genetic selection marker. The transformation efficiency of electroporation was almost 400 times more efficient than that of the lithium acetate method. While incorporation of DNA, flanked by a sequence endogenous to C. oleophila, transpired apparently by homologous recombination, the integration of DNA (that did not contain C. oleophila DNA) occurred at random. Whereas transformants were observed with a linear segment of the plasmid, none were detected with the undigested plasmid. This system provides both a tool for the molecular analysis of the biocontrol mechanism of C. oleophila and a means of tagging C. oleophila for field studies.