SELECTION OF YEAST-CELLS WITH A HIGHER PLASMID COPY NUMBER IN A SACCHAROMYCES-CEREVISIAE AUTOSELECTION SYSTEM

Autoselection systems allow the selection of a genetically engineered population independently of the growth medium composition. The structu re of a Saccharomyces cerevisiae population transformed with an autose lection plasmid, in which a carbon-source-dependent modulation of the plasmid copy number occurs, was analysed. By means of flow cytometric procedures we tested the cell viability, dynamics of growth and hetero logous protein production at single cell level. Such analyses allow th e identification and the tracking of a specific cellular sub-populatio n with a higher plasmid copy number which arises after the carbon sour ce shift. The effects of the cellular plasmid distribution on the dyna mics of growth are also discussed.