The effects of C7-alkylhydroxybenzene (C7-AHB) and p-hydroxyethylphenol (tyrosol), chemical analogs of microbial anabiosis autoregulators, on the viability of yeast cells under oxidative stress were investigated. The stress was caused by reactive oxygen species (ROS) produced under gamma irradiation of cell suspensions using doses of 10-150 krad at an intensity of 194 rad/s or by singlet oxygen generated in cells photosensibilized with chlorin e6 (10 micrograms/l). C7-AHB was found to exert a protective effect. The addition of 0.05-0.16 vol% of C7-AHB to cell suspensions 30 min before irradiation protected yeast cells from gamma radiation (50 krad). The protective effect of C7-AHB manifested itself both in the preservation of cell viability during irradiation and in the recovery of their capacity to proliferate after irradiation. In our studies on photodynamic cell inactivation, the fact that the phenolic antioxidant C7-AHB protects cells from intracellular singlet oxygen was revealed for the first time. The analysis of difference absorption spectra of oxidized derivatives of C7-AHB demonstrated that the protective mechanism of C7-AHB involves the scavenging of ROS resulting from oxidative stress. The fact that tyrosol failed to perform a photoprotective function suggests that the antioxidant properties of microbial C7-AHB are not related to their chaperon functions. The results obtained make an important addition to the spectrum of known antioxidant and antistress effects of phenolic compounds.