A Comprehensive Radiobiological Characterization of Anhydrobiotic Saccharomyces cerevisiae

The anhydrobiotic (living without water) yeast Saccharomyces cerevisiae has gained considerable interest for its use in a variety of fields, from investigation of the biological effects of deep space radiation exposure to its utilization as a radiation dosimeter and its applicability in the study of preservation of microbial life in martian regolith. A complete radiobiological characterization of yeast during anhydrobiosis must be undertaken to ensure the informed interpretation of these works. This study investigated the radiobiological properties of a desiccated recombinational repair-deficient rad51 knockout strain of S. cerevisiae. We focused on radiation tolerance, oxygen enhancement ratio (OER), and relative biological effectiveness (RBE). Desiccation-induced radioresistance was significantly higher compared with hydrated yeast; it required a threefold higher dose for an equivalent biological response. Desiccated yeast exhibited no OER, which indicates the absence of oxygen-dependent radiosensitization due to the lack of indirect damage pathways. RBE measurements for a 74 MeV proton beam (1.10 ± 0.01) and a neutron beam (12.2 ± 0.7) align with prior studies and demonstrate consistency between desiccated and hydrated systems when appropriately scaled. These findings support the use of the desiccated yeast model as a robust and translatable system for addressing fundamental questions in astrobiology and radiobiology.