Transformation of the yeast, Saccharomyces carlsbergensis, using an antibiotic resistance marker.

Transformation of the yeast, Saccharomyces carlsbergensis, with plasmids carrying the kanamycin (G418) resistance gene of Tn903 was attempted. Transformants resistant to the antibiotic, G418, were obtained from two strains of this species as well as a strain of S. cerevisiae after treatment of intact cells with lithium acetate and polyethylene glycol. The optimum period of post-incubation for expression of the kanamycin resistance gene was found to be four hours at 30°C for both S. carlsbergensis and S. cerevisiae. The transformation efficiency of S. carlsbergensis was lower than that of S. cerevisiae. The mitotic stability of the four plasmids used was determined; that of a plasmid containing the replication origin of 2 μm-DNA was lower in S. carlsbergensis than in S. cerevisiae. The mitotic stabilities of the three other plasmids containing ars 1, a centromere and ars 1, and no replication origin, respectively, in yeast cells were almost the same in S. carlsbergensis and S. cerevisiae.