A microorganism found everywhere there is life.
AOB is short for Ammonia-Oxidizing Bacteria, and they're found everywhere there is life: lakes, rivers, soil, and (formerly) on our skin.
By applying them back to your skin, you're restoring your skin to a native, healthy state.
Nitrite helps keep bad bacteria in check and Nitric Oxide is an antioxidant that helps calm and soothe the skin. This action can help restore balance to the skin's ecosystem and in turn reduce dependence on conventional products like soaps, moisturizers, and deodorants.
If you think you don't sweat enough, think again. We're all sweating, all the time, even if you don't feel it.
They're naturally regulated by the amount of sweat the body produces. If there is not enough food for all the AOBs in a given area, they will die (sadly). This regulation mechanism by your own sweat production is one of the many things that makes them incapable of causing an infection.
So don't worry about getting a spritz in your eye or mouth, there's nothing to be concerned about there (other than a salty aftertaste - yum.)
In fact, AOB are so influential that they only need to be present in small amounts to have an effect on your skin's microbial ecosystem: helping keep the bad in check and allowing the good to flourish.
Wiping them out is not harmful on its own. Instead, not having a way to repopulate the good guys that we've lost is what causes the longer term challenges. When the peacekeepers are wiped out, it becomes easier for the bad guys to have a stronger presence. This is why the best time to apply AOBs is after showering, using conventional products, or swimming in pools, etc.