Transformation of Kluyveromyces fragilis.

For the transformation of the yeast species Kluyveromyces fragilis, we have constructed a vector containing a bacterial kanamycin resistance (Kmr) gene, the TRP1 gene of Saccharomyces cerevisiae, and an autonomously replicating sequence of Kluyveromyces lactis called KARS2 . By utilizing the method based on treatment by alkali cations and with the Kmr gene as the selective marker, a wild-type strain of K. fragilis was transformed to resistance against the antibiotic G418 . In the transformed cell the plasmid replicates autonomously. The same plasmid could also be used to transform S. cerevisiae trp1 mutant to Trp+. Thus, KARS2 of K. lactis enables the vector to replicate in K. fragilis, K. lactis, and S. cerevisiae, whereas ARS1 of S. cerevisiae allows autonomous replication only in S. cerevisiae.