[Concurrent effect of ultraviolet rays of various wave lengths on Saccharomyces cerevisiae survival]

While studying the combined action of different UV wavelengths on Saccharomyces cerevisiae (strains XII and Cl-9), it has been found that preliminary irradiation with UV at 334 nm caused photoprotection of the cells against the lethal action of UV at 254 and 313 nm. Postradiation irradiation of strain XII incapable of photoreactivation with UV at 334 nm increased the lethal action of UV at 254 and 313 nm. The mechanisms of the both effects are based on serotonin synthesis induced by the light at 334 nm, as was shown using p-chlorophenylalanine, a specific inhibitor of serotonin synthesis. In strain CI-9 capable of photoreactivation, the postradiation effect of the light at 334 nm depends on the interaction of two different photobiological reactions induced by it, namely, photoreactivation and induced serotonin synthesis.