effect of the water activity of the growth medium on pesticide sensitivity in saccharomyces cerevisiae and S rouxii

ABSTRACT

Yeast cells of Saccharomyces cerevisiae and the osmotolerant yeast S. rouxii were grown aerobically and anaerobically on media the water activity of which was regulated either by sodium chloride or glycerol. The yeast cells were washed and suspened either in isotonic solutions of either solutes or in distilled water. Cells were then exposed to three pesticides namely the fungicide Antracol, the insecticide Supracide, and the akaricide Akar. Results were expressed as D-values [Decimal death time i.e, time in minutes required to kill 90% of cells]. Results showed that Supracide exerted the higest toxicity on both yeasts, followed by Akar, while Antraclo was the least toxic. Also, cells of S. cerevisiae showed higher response to the water activity of the growth medium in relation to pesticide sensitivity over S. rouxii in presence of either sodium chloride or glycerol