(A) Denitrification: The process of conversion of nitrates and nitrites into molecular nitrogen in the presence of denitrifying bacteria such as Thiobacillusdenitrificans is called Denitrification.
(B) Nitrogen fixation: The conversion of atmospheric, industrial, or biological nitrogen into such usable forms which can be utilized by living organisms is called Nitrogen fixation.
(C) Ammonification: The decomposition of proteins of dead animals and plants to ammonia in the presence of ammonifying bacteria such as Bacillusramosus and Bacillus vulgaris.
(D) Nitrification:
The process of oxidation of ammonia into nitrites and nitrates in the presence of nitrifying bacteria such as Nitrosomonas and Nitrobacter.
The ammonia is first oxidized into nitrite in the presence of Nitrosomonas bacteria and this nitrite is further oxidized to Nitrate in the presence of Nitrobacter bacteria.
