Which lifeforms can most support radiation and how do simplest mutate?

Question

Viruses, bacteria...?

Answer 1

http://scienceandreason.blogspot.com/2006/10/self-resurrecting-bacteria.html

tells about Deinococcus radiodurans, which can survive doses of radiation up to 500 times that which would kill a human

http://www.pcabusers.net/forums/archive/index.php/t-46974.html

is about a fungus that uses ionizing radiation the way plants use light.

Answer 2

There are many very simple lifeforms, nut the simplest is probably a miniscule single-cellular organism that would probably live in the sea, because it has the best chance of survival there. Basically, some of the stuff whales eat.

Answer 3

cockroaches
don´t know about the others