Write a note on the methods of nitrogen fixation in nature.
Answers
Nitrogen fixation is a process by which nitrogen in the Earth's atmosphere is converted into ammonia (NH3) or related nitrogenous compounds.[1] Atmospheric nitrogen, which is molecular dinitrogen (N2), is relatively nonreactive and is metabolically useless to all but a few microorganisms. The fixation process converts N2 into ammonia, which is metabolized by most organisms.
Nitrogen fixation is essential to life because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing compounds. Therefore, as part of the nitrogen cycle, it is essential for agriculture and the manufacture of fertilizer. It is also, indirectly, relevant to the manufacture of all chemical compounds that contain nitrogen, which includes explosives, most pharmaceuticals, and dyes. Nitrogen fixation is carried out naturally in the soil by a wide range of nitrogen fixing Bacteria and Archaea, including Azotobacter. Some nitrogen-fixing bacteria have symbiotic relationships with some plant groups, especially legumes. Looser relationships between nitrogen-fixing bacteria and plants are often referred to as associative or non-symbiotic, as seen in nitrogen fixation occurring on rice roots. It also occurs naturally in the air by means of NOx production by lightning.[2][3]
All biological nitrogen fixation is effected by enzymes called nitrogenases. These enzymes contain iron, often with a second metal, usually molybdenum but sometimes vanadium. Microorganisms that can fix nitrogen are prokaryotes (both bacteria and archaea, distributed throughout their respective domains) called diazotrophs. Some higher plants, and some animals (termites), have formed associations (symbiosis) with diazotrophs.