Yes. There are bacteria that live in volcanic vents. The types in our aquariums, however, do not. They are hardy, but they are hardly invincible. They do need oxegenation to thrive. But during a power outage the important thing is for them to live and do their job, not necessarily thrive. They will live and do their job, so long as the outage is not prolonged for extended periods of time. As I eluded too in my previous post, a simple battery operated air pump will solve this potential problem, and maybe eliminate stresss for the fish keeper. If the power goes out, fire up the pump with a little airline tubing and put the filter media near the bubbles. This will oxegenate both your bacteria in your filter, some in your tank, and also help to keep temperature from rising to high (if you are in a hot area). If the outage is going to be a day or two, don't worry. If it's going to be longer or you are paranoid about your bacteria, fire up the air pump.
\Dan