INFLUENCE OF GLUCOSE AND OTHER SUBSTRATES ON ELECTRIC-FIELD AND POLYETHYLENE GLYCOL-MEDIATED TRANSFORMATION OF INTACT YEAST-CELLS

A prepulse incubation with 2% glucose (mannose, fructose) strongly inh ibited electrotransformation of intact yeast cells. This inhibitory ef fect was not due to alterations of cell viability or to cell membrane electropermeabilization, and was not affected by the solution buffer p roperties of preincubation and pulsing media. The electrotransformatio n efficiency was not modified by non-metabolized substances, such as s orbitol or alose. The glucose inhibition of electrotransformation was fast, occurring after only a 3-5-min preincubation. The postpulse incu bation with substrate also decreased transformation efficiency, but wa s pH-dependent. We observed a similar, strong inhibitory effect of glu cose when cells were transformed chemically. A pH dependence of yeast electrotransformation was established.