5. What mechanisms do bacteria utilize to repair damage caused by radiation?

Answer 1

Hi:
The hardiest radiation resistant organism is Deinococcus radiodurans. Affectionately known to microbiologists as "Conan the Bacterium". A 500 to 1,000 rads radiation dose is enough to kill a human. Our hero survives1,500,000 rads.
It is a polyextremophile organism, that is found in cow dung and elephant sh it.
This bug survives environments that have no water, for months and does not shrivel up. It also is extremely resistant to oxygen levels that would fry us and most other bacteria.
So how does it survive?
Its genome has just been recently completely characterised. They found that it has a huge number of copies of its D.N.A.. It has superefficient nucleic acid correction enzymes, like D.N.A. polymerase. And it has a huge number of those enzymes.
The bug simply repairs its genome using the few intact stretches of its D.N.A. as a template to repair all the corrupted D.N.A. sequences, and broken up sections. Eventually a complete sequence is reconstruction and then the copying begins. There are other correction mechanisms that are not known yet. Which probably includes chaperone enzymes, and proteins that aid in the bug's ability to survive extreme conditions.
I suspect that D. radiodurans has the same sulfur stabilising cross linkages, in its enzymes, that stabilise similar enzymes in thermophilic bacteria. (water tempertures greater than boiling.)
Hope that helps
Dan the Answers-Man.