This slime, a collection of several fungi actually, was more than just surviving in a radioactive environment, it was actually using gamma radiation as a food source. Samples of these fungi grew significantly faster when exposed to gamma radiation at 500 times the normal background radiation level. The fungi appear to use melanin, a chemical found in human skin as well, in the same fashion as plants use chlorophyll. That is to say, the melanin molecule gets struck by a gamma ray and its chemistry is altered. This is an amazing discovery, no one had even suspected that something like this was possible.
Inside the reactor relic nothing should be alive: