Answer:
Bacteria are very important in the nitrogen cycle because they are responsible for fixing the inorganic nitrogen that is free in the atmosphere in organic nitrogen, which enters the terrestrial trophic networks and leaves them in the form of nitrogenous wastes that go to ground. Bacteria transform molecular nitrogen into ammonia, a form of nitrogen that can be used by plants.
Other bacteria called nitrifying bacteria transform ammonium into nitrite, and then nitrate
