Re: tech/campaign idea: bio-gel batteries
Most likely: the bacteria die on contact with free oxygen. I'd expect anything that could do this would be obligate anaerobes.
If you're looking for a nightmare scenario, then assert they can survive in sea water, and their electricity-producing effects stem from oxidizing iron. In their biogel cell, that iron is recycled by symbiosis with some iron-reducing bacteria (which use light) to recreate the elemental iron from the ferric oxide ... these iron-reducing guys die off when the cell wall is broken. The oxidizers get into the ocean, go nuts, and chew up all the iron & steel there. Their reservoir is old shipwrecks, but the thing they do that's apparent is dissolving ship hulls, drilling-rig platforms, etc. When multiple supertankers a week break apart and release their cargo into the ocean, I expect that'd get noticed....