 Nitrogen fixation is a process by which nitrogen in the Earth's atmosphere is converted into ammonia NH3 or other molecules available to living organisms. Atmospheric nitrogen or molecular dinitrogen and to its relatively inner, it does not easily react with other chemicals to form nude compounds. The fixation process frees nitrogen atoms from their trickly bonded diatomic form, N equals N, to be used in other ways. Nitrogen fixation is essential for some forms of life because inorganic nitrogen compounds are required for the biosynthesis of the basic building blocks of plants, animals and other life forms, e.g. nucleotides for DNA and RNA, the coenzyme nicotinamide adenine dinucleotide for its role in metabolism transfer and electrons between molecules and amino acids for proteins. 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 eyes. Nitrogen fixation is carried out naturally in the soil by a wide range of nitrogen fixing bacteria and archaea, including azotebacter. Some nitrogen fixing bacteria have symbiotic relationships with some plant groups, especially legumes. Booster 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 NICS production by lightning. All biological nitrogen fixation is done by way of metalloenzymes called nitrogenesis. These enzymes contain iron, often with a second metal, usually malignant but sometimes nadium. Micro-organisms 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.