| Module |
| M00175 | Nitrogen fixation, nitrogen => ammonia |
| M00528 | Nitrification, ammonia => nitrite |
| M00530 | Dissimilatory nitrate reduction, nitrate => ammonia |
| M00531 | Assimilatory nitrate reduction, nitrate => ammonia |
| M00621 | Glycine cleavage system |
| M00804 | Complete nitrification, comammox, ammonia => nitrite => nitrate |
| M00973 | Anammox, nitrite + ammonia => nitrogen |
| M00978 | Ornithine-ammonia cycle |
|