Ionizing Radiation Resistant Microorganisms
Kelley R. Gwin and John R. Battista
from: Extremophiles: Microbiology and Biotechnology (Edited by: Roberto Paul Anitori). Caister Academic Press, U.K. (2012)
Of all the phenotypes associated with microorganisms, ionizing radiation resistance - the ability to survive exposure to high dose gamma radiation - is perhaps the most difficult to rationalize in terms of the natural world. There is no obvious selective advantage to being ionizing radiation resistant on Earth, as average yearly exposures to ionizing radiation from cosmic rays and radioactive decay are extremely low. Yet a significant number of genera exhibit this characteristic, displaying a remarkable capacity to tolerate levels of damage to cellular macromolecules that eradicates other forms of life. We argue that ionizing radiation resistance is an incidental characteristic, an inadvertent consequence of an evolutionary path that permitted these species to survive a selective pressure capable of damaging the cell in a manner similar to that of ionizing radiation. The phylogenetic distribution of ionizing radiation resistant species argues that these events occurred multiple times during the evolution of the Bacteria and Archaea, suggesting that different mechanisms may mediate ionizing radiation resistance read more ...