It could never be found until recently, in a fish tank a few floors below a university microbiology department: one single organism able to perform the complete process of nitrification.

Chemolithoautotrophic nitrite-oxidizing bacteria (NOB) gain energy from the oxidation of nitrite to nitrate, which is the second step of nitrification and thus represents a major biogeochemical ...

The authors have discovered that nitrite-oxidizing organisms can convert cyanate (an oxidation product of cyanide and a decomposition product of urea) into ammonium (the protonated form of ammonia) ...