Nitrogen Cycle 2023

The Nitrogen Cycle

Nitrogen Fixation

When lightning strikes it converts the nitrogen gas in the air into nitrates which are washed into the soil as it rains. This is called nitrogen fixation.

Nitrogen

Nitrogen forms about 78% of the air in our atmosphere. It exists as a diatomic gas (N2). Most living organisms cannot use nitrogen in this form.Nitrogen is needed to make proteins, nucleic acids (DNA and RNA), hormones, antibodies, chlorophyll, and haemoglobin.

Nitrogen fixation

Some bacteria can convert nitrogen gas into nitrates. They are called nitrogen fixing bacteria.Examples: Rhizobium, Clostridium, Azotobacter

Denitification

Denitrifying bacteria convert nitrates back to nitrogen gas and release it into the atmosphere. Example: Pseudomonas, Achromobacter

Decomposition (Ammonification) When animals and plants die, decomposers (fungi and bacteria) break down the dead bodies and release ammonium compounds (NH4+). Example: Bacillus

Bacteria in the soil convert the ammonium compounds to nitrates. This occurs in a two step process.Step 1: Convert ammonium compounds to nitrites. Step 2: Convert nitrites to nitrates.

Nitrification

Nitrogen is an essential element found in all living organisms. This video summaries how nitrogen is recycled on earth.