Michael Daly (Uniformed Services University of the Health Sciences), Jim Fredrickson (PNNL) and others have published a paper in Science Express (http://www.sciencemag.org/content/306/5698/1025.abstract) on 30 October 2004 tying the extreme radiation resistance of Deinococcus radiodurans to high levels of manganese and low levels of iron. In the past, researchers have suggested that this microbe's extraordinary hardiness might be related to the unusual ring-like structure of its genome or the 4-8 genome copies carried by each cell. Daly and colleagues now show that chromosome organization is unlikely to play a role in radiation resistance and that a high concentration of manganese ions relative to iron ions is essential to its ability to survive gamma radiation. The authors suggest that the manganese may not provide protection from the initial radiation; rather, it protects cells against harmful reactive oxygen species that accumulate during the recovery from radiation.
"Secret of Radiation-Proof Bugs Proposed" Nature 30 September 2004 https://www.nature.com/news/2004/040927/full/040927-18.html