SLOW GROWTH PHENOTYPE - A POSSIBLE APPROACH TO IMPROVED PLASMID MAINTENANCE IN SACCHAROMYCES-CEREVISIAE

Transformation-induced slow growth phenotype (SGP) in yeast is repress ed in the presence of 2 mu m plasmids. A full 2 mu m-sequence-based re combinant plasmid (pJB502) was found to be more stable in a 2 mu m-fre e- [cir(o)] strain of Saccharomyces cerevisiae than in a cir(+) strain . This could not be attributed to differences in growth rate calculate d from kinetic analysis of plasmid loss, but transformed [cir(o)] isol ates, which had lost the recombinant plasmid, exhibited varying degree s of SGP in batch culture. One of these isolates was outcompeted in ch emostat culture by the recombinant-plasmid-containing strain, suggesti ng that improved plasmid maintenance can result from SGP in cir(o) hos ts.