Transformation

The key to the molecular genetic manipulation of any organism is the ability to introduce and maintain DNA sequences of interest. For Pichia pastoris , the fate of introduced DNAs is generally similar to those described for Saccharomyces cerevisiae . Vectors can be maintained as autonomously replicating elements or integrated into the P. pastoris genome (1 –4 ). As in S. cerevisiae , integration events occur primarily by homologous recombination between sequences shared by the transforming vector and P. pastoris genome (1 ). Thus, the controlled integration of vector sequences at preselected positions in the genome via yeast gene targeting and gene replacement (gene knockout) strategies are readily performed in P. pastoris (2 ).