Bacteria
Explanation:
Nitrification fixation takes place by nitrogen-fixing bacteria like Azotobacter, Klebsiella, Bacillus etc which convert atmospheric nitrogen gas into fixed-nitrogen compounds like nitrates or ammonium ions for the plants to readily absorb.
The nitrogen fixing bacteria can be free-living like cyanobacteria or live with symbiotic relationship with plants and fungi.
The chemical conversion of di-nitrogen to ammonia takes place with the help of enzymes like nitrogenase in combination with leghahemoglobin, a protein through a reduction reaction.
