If conditions within an organism's environment occasionally or regularly become harsh, it may be advantageous for an organism to have a resistant stage built into the life cycle.
Deinococcus radiodurans, as a model organism in DNA damage and repair, is the most resistant bacterium to ionizing radiation.
耐辐射奇球菌作为 DNA 损伤和修复的典范生物，是对电离辐射最有抵抗力的细菌。
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Susceptible strains can become resistant either through mutations in existing genes or by acquiring a resistance gene from another organism that is already resistant.