* Bacteria: Bacteria are the primary organisms responsible for the nitrogen cycle. They convert atmospheric nitrogen into ammonia, which is then used by plants for growth. Bacteria also convert ammonia into nitrite and nitrate, which are also used by plants.

* Archaea: Archaea are a type of microorganism that are similar to bacteria. They also play a role in the nitrogen cycle by converting ammonia into nitrite and nitrate.

* Fungi: Fungi help to decompose organic matter, which releases nitrogen into the soil. Fungi also form symbiotic relationships with plants, helping them to absorb nitrogen from the soil.

* Plants: Plants use nitrogen for growth. They absorb nitrogen from the soil in the form of nitrate and nitrite.

* Animals: Animals consume plants and other animals, which releases nitrogen into the environment. Animals also excrete nitrogen in their urine and feces.