Photosensitization of Saccharomyces carlsbergensis by Rose Bengal

Abstract

When suspensions of S. carlsbergensls Hansen containing rose bengal at a concentration 6F2 x 10-5 [image] were exposed to light of 2200 ft-c intensity for 1 hour at 25[degree]C a lethaflFy between 82 and 100% was obtained. When the time of illumination was varied, 10% kill was obtained after a 5 min. exposure, 85% after 15 min., and 97% after 40 min. After 80 min. the kill was 99-100%. No kills were observed in nonaerated cultures. A definite correlation was obtained between the amount of killing and the stage of budding of a synchronously dividing yeast culture. Percentage kill increased as buds began to form, reached a maximum when buds were fully formed, and decreased as daughter cells matured. An apparent protective effect of nutrients was noted when the cells were exposed to dye and light in the presence of culture medium rather than buffer.