Microbiology Procedure

Index >>Nitrogen Fixation >>Denitrification

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Nitrogen Fixation Nitrogen Fixation Part 1 Structure of Nitrogenase Components Fe Protein Mo-Fe Protein Mechanism of Nitrogenase Action Hydrogen Evolution Factors Affecting Nitrogenase Activity Nitrogen Fixation Genes Nitrification Nitrate Reduction Glutamate Synthase Pathway

Denitrification

	Denitrification - Many aerobic bacteria can grow anaerobically, using nitrate as the final electron acceptor. This process is known as nitrogen respiration. Nitrate reduction products include nitrite and various other forms of nitrogen. Some Bacillus spp. can carry out anaerobic respiration in which nitrate is reduced to ammonia. This process is called nitrate reduction, and has been described earlier. When the product of nitrate respiration is nitric oxide, or nitrous oxide or dinitrogen, the process is called denitrification. In synthetic media for denitrifying bacteria, nitrate is included as a terminal oxidant. Lactate or malate provides the best source of carbon and energy. When nitrate is used as an electron acceptor, there is net loss of nitrogen from the soil. This process is therefore known as dissimilatory nitrogen reduction.
Denitrification takes place in two steps. In the first step, two electrons are added to nitrate resulting in the formation of nitrite. NO^-₃ + 2e^- -+ 2H --> NO^-₂ + H₂O Nitrite is ultimately reduced to molecular nitrogen, which is the usual major end product of denitrification. Under certain conditions, however, there is addition of two further electrons per nitrogen atom, resulting in the formation of nitrous oxide (N₂O) from nitrate. 2 NO₂ + 4H+ -->N₂O + H₂O + 2 OH^-
Nitrous oxide can also be reduced to molecular nitrogen by denitrifying bacteria. N₂O +2H+-->N₂+ H₂O All denitrifying bacteria can use nitrite instead of nitrate for denitrification. Nitrite can give rise to N₂ directly or through N₂O. It has been suggested that the formation of N₂, or N₂O from nitrite involves an in termediate of composition N₂O₂H₂ through NOH (nitroxyl).

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Nitrogen Fixation Part 1 Ammonification Denitrification Denitrifying Bacteria Ecological Importance of Denitrification Nitrogen Assimilation Transamination Glutamate Dehydrogenase (GDH) Glutamate Synthase Pathway Glutamine Synthetase (GS) Reaction Glutamate Synthase (GOGAT) Reaction Transaminase Reactions Glutamine Synthtase Adenylylation and Deadenylylation

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