Dark recovery phenomena in the pathogenic yeast Torulopsis glabrata irradiated by ultraviolet light

The capacity of Torulopsis glabrata (T. glabrata) (a mycomycetes) separated from human oral cavity to recover from ultraviolet injuries were investigated. When cells irradiated with ultraviolet rays were kept in purified water at 270C before planting cells on agar culture medium for colony formation, survival rate of cells recovered according to an increase in the period of liquid holding. The recovery of the survival rate of cells at logarithm proliferation stage was higher than that of cells at normal stage. The time necessary for the recovery of the survival rate of cells exposed to ultraviolet ray by liquid holding became longer according to an increase in exposure dose. Caffeine reduced the survival rate of cells exposed to ultraviolet ray specifically when it was added with the concentrations which did not influence the survival rate of non-exposed cells at all. This suggested that caffeine acted on ultraviolet injuries of DNA. The recovery of the survival rate of cells was inhibited when caffeine was added during liquid holding. However, the effect of caffeine to inhibit the recovery of the survival rate was reduced when caffeine was added after liquid holding. Therefore, it was recognized that caffeine acted on as an inhibitor against DNA repair. Abovementioned recovery of the survival rate of cells by liquid holding and the effect of caffeine to inhibit DNA repair resembled the results in other living bodies having dark recovery capacity, which suggested that T. glabrata had the capacity to repair DNA. (Tsunoda, M.)