Denitrifying bacteria are those bacteria that can convert the nitrate into free nitrogen. These bacteria consume the soil nitrate and convert into free nitrogen thus decrease the fertility of the soil.

Examples of denitrifying bacteria:

Pseudomonas aeruginosa, Thiobacillus denitrificans.

Habitat:

These bacteria are usually present in water, sediments and soils. There is a great diversity of the denitrifying bacteria. Over 125 species are identified that can convert nitrate into free nitrogen.

Denitrification Equation:

These bacteria under anaerobic condition reduce the nitrate to produce free nitrogen and generate energy. This energy is taken up by bacteria for its metabolism.

2 NO^-3 + 10 e^– + 12 H⁺ → N₂ + 6 H₂O

These reactions are carried out by 3 different enzymes.

• Nitrate reductase enzymes converts nitrate into nitric oxide.
• Nitric oxide reductase converts nitric oxide into nitrous oxide
• Nitrous oxide converts nitrous oxide into nitrogen

These reactions are carried out by the bacteria that have these enzymes mentioned above.

Importance:

• These bacteria are ecologically important as they reduce the fertility of the soil.
• These bacteria play a role in the nitrogen cycle as they deplete the nitrate from the soil
• These bacteria produce by-products that increase global warming.