Let's first take a quick look at what radiation does to a living thing. No creature can survive without its genes in working order. D. radiodurans , on the other hand, can stitch back together DNA shattered to bits by radiation within a matter of a few hours. One reason is that it has lots of extra copies of its genes. D. radiodurans cells have four to ten copies of their DNA molecule.
Most bacteria have only one copy.
So when radiation hits and D. radioduran's DNA gets busted up, the microbe has lots more chances of finding an intact copy of each gene to use as it stitches its DNA back together. A special protein called RecA does the stitching. Also, it appears that D. radiodurans may have more of the cell repair tools that most bugs have. After all, other microbes have many of the same tools, although not in as high numbers and variety as D. radiodurans does. And some other bacteria have more than one copy of their genes, although none have quite as many copies as D. radiodurans .