Nitrogen fixers
Nitrogen is important for all organisms since it is one of the components of proteins and nucleic acids (DNA).
Most living species cannot directly absorb nitrogen from the atmosphere, of which this gas is the largest component (78%). Only some bacteria can transform gaseous nitrogen into compounds that can be absorbed by the other living beings (especially vegetal organisms) through a series of metabolic reactions that are jointly called “nitrogen fixation”. Nitrogen, included in more complex molecules, such as ammonia and nitrates, is part of the food chain. The most important nitrogen-fixing organisms are cyanobacteria, also known as blue algae, which live in water. On the mainland, this function is mainly served by the Azotobacter that live son earth and by the Rhizobium that lives in symbiosis in the roots of the plants of the genus Leguminosae (bean, lentil and clover).
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