Wow, that's a lot of questions!

First off, no organism, bacteria or otherwise, can survive in a pure oxygen environment. Viruses can't survive very long on their own, and in order for viruses to reproduce, they need living hosts nearby for them to infect.

In your scenario, the pure oxygen environment would quickly kill the bacteria, and so the virus would "die" too, eventually. (I say "die" in quotes because many scientists do not think viruses are alive, and if viruses aren't alive, then they can't die. Personally, I think viruses ARE alive, but it's sort of a philosophical question about how you define life.)

The pure oxygen environment probably wouldn't kill the virus itself, since viruses don't have all the chemical processes (metabolism) going on inside them that every other living organism does.

Pure oxygen would poison any organism that depends on chemical reactions for life (basically, every organism except viruses). Most viruses can only infect one type of organism (a human, a cat, a cow, a plant, a bacteria). However, no matter what organism you put into a pure oxygen environment, it would die, so the virus would as well, since it can't reproduce without it's host and it can't survive too long on it's own.Here's another scenario: Imagine if you built an enclosed fish tank, with plants for oxygen and many different marine organisms so that there was enough food for the fish to eat. Now imagine that you were able to remove ALL the viruses from this fish tank, even the viruses floating in the sea water and in the air at the top of the tank. (This would be impossible to do, but we're just imagining here.) If the fish tank was really closed to outside air, then the plants and animals in tank would never be infected by a virus ever. Now imagine if you could introduce just ONE virus, a virus that infects one type of bacteria floating in the seawater. Every plant and animal in that tank could co-exist happily with the virus except the bacteria, which would become infected. You could almost argue that even the population of bacteria being attacked by the virus could co-exist in harmony with the virus, since the virus wouldn't kill ALL of the bacteria, just a few. If viruses killed ALL their hosts, they'd quickly make themselves extinct.