New type of symbiosis: Bacteria eat ammonia in fish gills

Microbiologists and fish researchers have discovered an entirely new type of symbiosis: bacteria in the gills of fish that convert harmful ammonia into harmless nitrogen gas. Fish produce a lot of ammonia, which is a waste product from their protein metabolism. Ammonia also pollutes the water in which they live, and in excessive concentrations can even be deadly. “We humans excrete excess ammonia in our urine, through urea. Fish do so through their gills,” explains a microbiologist.