If you just want to read about the bug, this was pretty interesting:
Biology of extreme radiation resistance: the way of Deinococcus radiodurans. - Cold Spring Harb Perspect Biol.
Biology of extreme radiation resistance: the way of Deinococcus radiodurans. - Cold Spring Harb Perspect Biol.
The main reasons are that they can transfer heat very easily and they do not contain much water relative to their volume.
So there is probably a lot more life that can withstand extreme conditions.