The nitrogen cycle represents
circulation and recycling of chemical
element nitrogen in .

The nitrogen cycle basicallydepends
the action of some bacteria.
Bacteria of the called nitrogen-fixing
bacteria present plant roots absorb
molecular from the air and
nitrogen in the form
ammonia. The decomposition of
material also produces ammonia. the
soil and roots ( of leguminous
plants), a group of chemosynthetic
bacteria nitrifying bacteria, the
nitrosomonas, energy
consuming ammonia and
nitrite (NO₂). The second of
nitrifying bacteria, the ,
uses nitrite in chemosynthesis
nitrate (NO₃). Inthe form nitrate,
nitrogen is then by plants
to be as constituent of proteins
nucleic acids and the then
follows along the chain. Nitrogen
returns to atmosphere by the action
denitrifying bacteria that use
-containing compounds from
the soil release nitrogen gas
(molecular ).