FLUENCE RATE AS A DETERMINANT OF SYNERGISTIC INTERACTION UNDER SIMULTANEOUS ACTION OF UV-LIGHT AND MILD HEAT IN SACCHAROMYCES-CEREVISIAE

In experiments with wild-type diploid yeast cells of Saccharomyces cer evisiae, the synergistic lethal action of a simultaneous application o f ultraviolet (UV) light (wavelength, 254 nm) and mild heat (45-57.5 d egrees C) was studied. It was shown that, at any fixed UV light intens ity, the synergistic effect occurred within the given temperature inte rval. The optimal temperature to achieve the greatest synergistic effe ct may be shown for every fluence rate examined. The correlation betwe en the optimal temperature that maximized the synergy and UV light int ensity was estimated: this temperature shifted towards higher temperat ure values with an increasing fluence rate. A possible interpretation of this effect is based on the supposition that the mechanism of the s ynergistic effect is related to additional lethal damage produced by t he interaction of sublesions induced by each agent. These sublesions a re supposed to be non-lethal when each agent is applied separately. (C ) 1997 Elsevier Science S.A.