Slow growth phenotype--a possible approach to improved plasmid maintenance in Saccharomyces cerevisiae

Transformation-induced slow growth phenotype (SGP) in yeast is repressed in the presence of 2 micromole plasmids. A full 2 micromole-sequence-based recombinant plasmid (pJB502) was found to be more stable in a 2 micromole-free- [cir] strain of Saccharomyces cerevisiae than in a cir+ strain. This could not be attributed to differences in growth rate calculated from kinetic analysis of plasmid loss, but transformed [cir] isolates, which had lost the recombinant plasmid, exhibited varying degrees of SGP in batch culture. One of these isolates was outcompeted in chemostat culture by the recombinant-plasmid-containing strain, suggesting that improved plasmid maintenance can result from SGP in cir hosts.