Some stages of the nitrogen cycle where bacteria have a high significance are:
1) Nitrogen fixing in the root nodules of legumes
Nitrogen fixing bacteria reside in the root nodules of leguminous plants, where they fix atmospheric nitrogen into forms of nitrogen usable by the plant.
2) Nitrogen fixation in the soil
Some nitrogen fixing bacteria live in the soil, converting atmospheric nitrogen to usable forms.
3) Decomposition
Bacteria also play a role in decomposing organic matter, where the complex nitrogen containing compounds present within organisms are converted to simpler forms of nitrogen and released into the soil
4) Nitrification
Bacteria present in the soil convert ammonium ions to nitrite ions
Moreover, other bacteria convert nitrite ions to nitrate ions
5) Denitrifying bacteria
These bacteria convert nitrogen in the soil to atmospheric nitrogen and release it from the soil
