Nitrogen is popularly known as most abundantly available element in earth atmosphere. Earth is large reservoir of nitrogen. It covers around up to 78% of total elements in the earth. The nitrogen available in the earth surface cannot be directly used, but it has to be converted to different forms. Nitrogen cycle is one of the most important protein cycle for the existence of different forms of life.
The DNA and RNA are made up of nitrogen. So inevitably this element is very necessary for the growth of life. So there is a chain of procedures involved in the formation of nitrogen. And nitrogen should be available in different compound forms for applications. The plant and animals involve in different procedures to convert nitrogen to required compounds. And by the decomposition of dead plants and animals these compounds are again converted to the original form. Thus the cycle repeats.
The nitrogen cycle is as follows
- Nitrogen Fixation
- NITROGEN FIXATION:
As known nitrogen is in the form of N2 i.e. in diatomic form. It is a bacterial activity. Since it cannot be used in the available form. This conversion of diatomic nitrogen into other compounds is done by the nitrogen fixing bacteria. These nitrogen fixing bacteria are found in the root part of legume plants like beans, alfalfa. The water on the soil surface breaks down the diatomic nitrogen and the nitrogen atom combines with hydrangea and forms ammonia ().
Most of the nitrogen is fixed by the prokaryotes but it is also fixed by natural phenomena such as lightning.
The nitrification process involves two steps i.e. ammonium is converted to nitrite at first and then converted to nitrate. The nitrification is majorly carried out by prokaryotes. Microorganisms play a very prominent role in this conversion. The oxidiser bacteria carries out oxidation of ammonia into nitrite.
Step1: This conversion process requires two enzymes namely ammonia monooxygenase and hydroxylamine oxidoreductase.
In the above equation first reaction is conversion of ammonia to intermediate products i.e. hydroxylamine. The second reaction is conversion of hydroxylamine to nitrite.
Step2: This step is oxidisation of nitrite to nitrate. In this step the oxidising is carried out by nitrite-oxidising bacteria. Nitrobacter, Nitrospira are some of the types of bacteria involved in conversion of nitrite to nitrate.
The above equation gives the conversion of nitrite to nitrate. And in both reactions bacteria gain energy and need oxygen for these reactions.
At this stage the animals and plants take up ammonia and nitrate from the initial two stages. So the plants absorb these compounds from soil via root hair. The nitrite is reduces to nitrate ions and ammonium ions for assimilating into amino acids, chlorophyll and nucleic acid. This stage is purely representing the use of the nitrites, nitrates and ammonia by plants and animals.
The dead and decayed plants and animals buried in the ground give all the nitrogen compounds back to soil. These remaining matter is known as urea. It forms good manure for the soil, which is rich in proteins. The decaying bacteria are responsible for converting ammonia and ammonium into soil. Further this available ammonia is used for biological processes.
Denitrification is the reverse process of nitrification. This stage is purely reduction process. The nitrogen compounds are reduced their original diatomic stage. This happens in severe anaerobic conditions. Pseudomonas and Clostridium are the bacteria responsible denitrification.
Nitrogen also finds many other uses in daily life activities.
Keywords: Nitrogen cycle, natural fixation, Bacteria, legume plants