Non-symbiotic Nitrogen Fixation

Non-symbiotic nitrogen fixation in soil indicates the procedure of fixing atmospheric nitrogen by various free-living microorganisms. Nitrogen is an essential component for the proper functioning of plant and animal bodies. Our atmosphere contains 78% of nitrogen. But, most organisms of plants cannot fix it directly. Certain microorganisms can convert atmospheric nitrogen into ammonia and then plants can use the nitrogen. Non-symbiotic nitrogen-fixation bacteria can be free-living nitrogen-fixing or non-symbiotic or they can be in a symbiotic relationship with certain plant species. Thus, nitrogen-fixing microorganisms play an important role in a plant’s survival.

What is Non-Symbiotic Nitrogen Fixation?

Non-symbiotic nitrogen fixation means fixing atmospheric nitrogen into soil by free-living microbes. The production of ammonia from the atmospheric nitrogen and then converting the ammonia into nitrite and nitrate (nitrification) are two major steps that occurred during this process.

Mechanism of Non-Symbiotic Nitrogen Fixation

The steps involved in nitrogen fixation by free-living microbes are described below:

At first, ammonia is created by the reduction of atmospheric nitrogen with the help of free-living nitrogen-fixing bacteria. Then nitrifying bacteria such as Nitrosomonas, Nitrosococcus, Nitrosospira, etc convert the ammonia into nitrite.

NH₃^– (Ammonia) → NO₂^– (Nitrite)

These nitrifying bacteria then convert nitrite into nitrate.

NO₂^– (Nitrite)→NO₃^–-(Nitrate)

Thus, free living nitrogen fixing bacteria fix atmospheric nitrogen into the soil. Plants absorb the nitrate from the soil and they can utilise nitrate (a compound of nitrogen) only to fulfil their nitrogen requirement in the body.

Denitrification

Denitrification is a process by which fixed nitrogen in the soil or the nitrate is converted into gaseous nitrogen. This phenomenon occurs to release the fixed nitrogen into the atmosphere again. Denitrifying microbes help in this process. Denitrification bacteia are Pseudomonas, Paracoccus, and Bacillus species. This process is essential for maintaining the soil fertility and health of plants and animals.

Non-Symbiotic Nitrogen Fixation Diagram

The following is a diagram of Non-Symbiotic Nitrogen Fixation:

Examples of Non-Symbiotic Nitrogen Fixing Bacteria

Some examples of Non-Symbiotic Nitrogen Fixing Bacteria are as follows:

• Aerobic: These bacteria can fix nitrogen in presence of oxygen. Some examples are: Azotobacter, Azospirillum, Chlorobium, etc.
• Anaerobic: These bacteria can fix nitrogen in absence of oxygen. Some examples are: Clostridium, Rhodospirillum, etc.
• Chemosynthetic: These bacteria can fix nitrogen through chemosynthesis. Some examples are: Klebsiella, Desulphovibrio, etc.
• Cyanobacteria: These are also known as blue-gren algae. These are all photosynthetic organisms and have specific structure called heterocyst that help them fix nitrogen. Examples include: Anaebena, Nostoc, Oscillatoria, etc.

Why is Nitrogen Fixation Important?

Nitrogen fixation by microbes is very essential for the survival of plants. It increases the nitrogen content of the soil without the use of fertiliser. Plants cannot absorb atmospheric nitrogen directly. They only utilise nitrate (a form of nitrogen). Nitrogen fixing bacteria converts atmospheric nitrogen into nitrate. Nitrogen in plants perform various major functions such as:

• Nitrogen is the major component of amino acids. Amino Acids are necessary for the production of various proteins in the plant body.
• Nitrogen is also essential for the generation of nucleic acids such as DNA, RNA in plants.
• Nitrogen is also essential for overall growth and development of plants.

Difference Between Symbiotic and Non-Symbiotic Nitrogen Fixation

The table given below summarises the difference between symbiotic and non-symbiotic nitrogen fixation.

Criteria	Non-Symbiotic Nitrogen Fixation	Symbiotic Nitrogen Fixation
State	This is carried out by free living micro-organisms.	This is carried out by organosms living in symbiotic association with higher plants.
Bacterial Species involved	Can include various bacterial groups like Azotobacter, Azospirillum, etc.	Typically involves rhizobia bacteria that form root nodules like Rhizobium.
Dependency of nitrogen fixers	The organisms are free living and do not depend on any higher plants.	The organisms depend on the host plant for energy.
Mutualism	Non-Symbiotic Nitrogen Fixation does not exhibits mutual relationship between participating organisms	Symbiotic Nitrogen fixation exhibits mutual relationship between teo organisms.

Conclusion – Non-Symbiotic Nitrogen Fixation

Nitrogen fixation is a process of fixing atmospheric nitrogen into the soil. Thus, plants can utilise atmospheric nitrogen in the form of nitrate. Nitrogen fixation can occur abiotically which means it can be done industrially or can occur by lightning. Besides this, nitrogen fixation can occur biotically with the help of nitrogen fixing bacteria. Nitrogen fixing bacteria can be symbiotic or can be free living. Non-symbiotic nitrogen fixation means fixing atmospheric nitrogen into soil by free-living microbes. These bacteria convert atmospheric nitrogen into nitrate. Plants use the nitrate to fulfil their nitrogen requirement in the body.

FAQs on Non-Symbiotic Nitrogen Fixation

Can Rhizobium Bacteria be considered as Non-Symbiotic Nitrogen Fixers?

No, Rhizobium bacteria is not a non-symbiotic microbe. It forms symbiotic relations with legume plants and helps in nitrogen fixation.

Name a Non-Symbiotic Nitrogen Fixing Microbe.

Azotobacter is a non-symbiotic nitrogen fixing microbe. It helps to fix atmospheric nitrogen into the soil.

Write the Difference Between Biological and Non Biological Nitrogen Fixation.

Non biological nitrogen fixation occurs industrially with the help of equipment or by lightning. But, biological nitrogen fixation occurs by microbes (mainly bacteria).

Write an Advantage of Nitrogen Fixation.

Nitrogen fixation means fixing atmospheric nitrogen into the soil. It increases the nitrogen content of the soil without utilising fertiliser.

What is Symbiotic Nitrogen Fixation?

Certain bacterial species form symbiotic or mutual relation with certain species of plants (mainly legume plants) and live in the root nodule or stem nodule of such plants. Thus, these bacteria help in nitrogen fixation and this process is called symbiotic nitrogen fixation.

Define Non-symbiotic Nitrogen Fixation?

Non-symbiotic nitrogen fixation refers to the process where certain free-living soil bacteria, like Azotobacter and Clostridium, convert atmospheric nitrogen into usable forms for plants without forming a symbiotic relationship with them.

How does Non-Symbiotic Nitrogen Fixation Differ from Symbiotic Nitrogen Fixation?

Non-symbiotic nitrogen fixation involves free-living bacteria like Azotobacter, while symbiotic nitrogen fixation occurs within specialized structures in plant roots, involving bacteria like Rhizobium.

What is the Difference Between Non-Symbiotic Nitrogen Fixation and Nitrogen Cycle?

Non-symbiotic nitrogen fixation converts atmospheric nitrogen into usable forms, while the nitrogen cycle involves the continuous cycling of nitrogen through various processes like fixation, nitrification, assimilation, and denitrification within ecosystems.

What are Non-Symbiotic Nitrogen-Fixing Biofertilizers?

Non-symbiotic nitrogen-fixing biofertilizers contain free-living nitrogen-fixing bacteria like Azotobacter and Azospirillum, increasing soil fertility and plant growth without forming symbiotic relationships with plants.