Radiotolerance

Radiotolerance refers to the relative ability of organisms, cells, or tissues to withstand ionizing radiation without sustaining lethal or mutagenic damage. It is a central concept in radiobiology and is distinct from radiosensitivity. Radiotolerance varies widely across life forms and depends on radiation dose, dose rate, radiation quality, and the biological characteristics of the exposed material.

Key determinants of radiotolerance include efficient DNA repair mechanisms, such as homologous recombination and non-homologous end joining, and robust systems for managing reactive oxygen species. Some organisms employ multiple genome copies or protective biochemical networks, including manganese-based antioxidants, to limit radiation-induced damage. Rapid, accurate reassembly of DNA fragments and checkpoint control of the cell cycle help cells survive radiation exposure.

Extremophilic microbes provide extreme examples of radiotolerance. Deinococcus radiodurans can survive doses far exceeding typical environmental exposures, due to its DNA repair capacity and protective cellular chemistry. Eukaryotic radiotolerance varies by tissue; in humans, whole-body exposure of about 4–5 Gy is lethal without treatment, with more sensitive tissues showing rapid decline. Other organisms, including certain tardigrades and plant varieties, exhibit notable resilience thanks to protective traits and effective repair pathways.

Research into radiotolerance informs medical radiotherapy, development of radioprotective agents, and biosafety planning. It also contributes to astrobiology and biotechnology, including the design of radiotolerant crops and the use of extremophiles for bioremediation in radioactive environments.