PHOTODYNAMIC INACTIVATION OF YEAST SENSITIZED BY EOSIN Y

Abstract

Abstract. Wild‐type diploid yeast has been irradiated with visible light in the presence of eosin Y to investigate the photodynamic inactivation of this model eukaryote. Light, eosin Y and oxygen were all required for substantial inactivation, and no dark recovery was detected. Long periods of irradiation were required for greater than 90% inactivation, corresponding to a very small low‐dose quantum yield. Neither binding nor uptake of the dye by yeast was detected. Corrections for the photooxidative bleaching of eosin Y during irradiation indicate that bleaching causes a significant reduction in the apparent rate of inactivation. The results suggest that eosin Y acts as an extracellular sensitizer where the likelihood of damage to the cell envelope is enhanced.