Nitrogen Fixation Definition, Bacteria, Example, Cycle and Diagram

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Nitrogen Fixation Definition

Molecular nitrogen (N₂) in the air, which has a powerful triple covalent bond, is changed into ammonia (NH₃) or other similar nitrogenous chemicals by a chemical process known as nitrogen fixation. This process normally occurs in soil or aquatic environments, although it can also occur in industry. Molecular dinitrogen, which makes up the majority of atmospheric nitrogen, is a generally nonreactive molecule that is biologically inert to most microbes. Utilizing the nitrogenase protein complex, biological nitrogen fixation, also known as diazotrophy, is a crucial microbially driven activity that changes nitrogen (N₂) gas into ammonia (NH₃).

Nitrogen Fixation

Because the creation of all nitrogen-containing organic chemicals, including as amino acids and proteins, nucleoside triphosphates, and nucleic acids, depends on fixed inorganic nitrogen compounds, nitrogen fixation is crucial for life. It is crucial for agriculture and the production of fertilizer as a component of the nitrogen cycle. Additionally, it has indirect implications for the production of all nitrogen chemical compounds, including some explosives, medications, and dyes.

In soil, diazotrophic microorganisms, which include bacteria like Azotobacter and archaea, fix nitrogen in a natural way. Some nitrogen-fixing bacteria coexist harmoniously with certain plant species, particularly legumes. As in the case of nitrogen fixation on rice roots, looser non-symbiotic connections between diazotrophs and plants are frequently referred to as associative. Some termites and fungus work together to fix nitrogen. It happens in the atmosphere on its own as a result of lightning-induced NO_x generation.

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Ways of Nitrogen Fixation

The primary source of food is plants. The many elements that plants use to create the nutrients that we get from plants come from both the soil and the atmosphere. Also included in this category of elements is nitrogen. Nitrogen is taken up by plants from the soil and used for protein synthesis. In contrast to carbon dioxide and oxygen, leaves’ stomata are unable to absorb atmospheric nitrogen. due to the fact that plants cannot directly use the atmospheric nitrogen gas. In order to fix nitrogen, some bacteria and other natural phenomena are required.

Biological Nitrogen Fixation

Ammonia can be produced from atmospheric nitrogen by specific bacteria and prokaryotes. The biological fixation of nitrogen is the name of this process. Dinitrogen is converted to ammonia by the enzyme nitrogenase. Free-living or symbiotic microorganisms that fix nitrogen are both possible. Azotobacter, Beijernickia, Rhodospirillum, cyanobacteria, and others are examples of free-living nitrogen fixers. Rhizobium, which is found in the root nodules of legumes, and Frankia, which is found in the root nodules of non-leguminous plants, are two examples of symbiotic nitrogen fixers.

Nitrogen Fixation by Lightning

Lightning is another activity that aids in nitrogen fixation. It is a natural occurrence where the energy of a lightning strike transforms nitrogen from an unusable form into one that may be absorbed. Even though lightning has a minor role in nitrogen fixation, it protects plants from a lack of vital nutrients.

Nitrogen Metabolism

Chemical reactions known as metabolism are used to transform chemicals into forms of useful energy. Ammonia (NH₃) is recycled into the neutral or charged form ammonium ion (NH₄⁺), which is the primary step in the metabolism of nitrogen. The Nitrogen Cycle is the primary component of nitrogen metabolism.

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Nitrogen Fixation Bacteria

Chemical reactions known as metabolism are used to transform chemicals into forms of useful energy. Ammonia (NH3) is recycled into the neutral or charged form ammonium ion (NH4+), which is the primary step in the metabolism of nitrogen. The Nitrogen Cycle is the primary component of nitrogen metabolism.

There are two identified types of bacteria that fix nitrogen. The cyanobacteria (or blue-green algae), Anabaena and Nostoc, as well as genera like Azotobacter, Beijerinckia, and Clostridium, are included in the first category of bacteria, the free-living (nonsymbiotic) bacteria. The mutualistic (symbiotic) bacteria make up the second type. Examples include Rhizobium, which is connected to leguminous plants (such different types of peas), Frankia, which is connected to some dicotyledonous species, and specific Azospirillum species, which are connected to cereal grasses.

Nitrogen Fixation Diagram

Nitrogen Fixation

Nitrogen Fixation Cycle

The nitrogen cycle is a biogeochemical process through which nitrogen is changed into a variety of forms before returning to the atmosphere after first entering the soil and then organisms. It involves a number of chemical reactions, including the fixation of nitrogen, nitrification, denitrification, decay, and putrefaction. Both organic and inorganic forms of nitrogen gas are known to exist. Living things contain organic nitrogen, which is transferred along the food chain when they consume other living things.

In the atmosphere, inorganic forms of nitrogen are prevalent. Symbiotic bacteria that can transform the inert nitrogen into useful forms, such as nitrites and nitrates, make this nitrogen available to plants.

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Stages of Nitrogen Fixation Cycle

Nitrogen fixation, nitrification, assimilation, ammonification, and denitrification are the steps that make up the nitrogen cycle.

The nitrogen cycle’s first stage is represented by it. Here, atmospheric nitrogen (N2) is transformed into ammonia, an useful molecule that is predominantly available in an inert form (NH3).
The inert form of nitrogen gas is deposited into soils during the nitrogen fixation process from the atmosphere and surface waters, primarily through precipitation.
Symbiotic bacteria known as diazotrophs finish the full nitrogen fixation process. A significant part of this process is also played by Azotobacter and Rhizobium. The nitrogenase enzyme found in these bacteria can combine gaseous nitrogen and hydrogen to produce ammonia.
Either atmospheric fixation, which includes lightning, or industrial fixation, which involves producing ammonia under extreme heat and pressure, are two ways that nitrogen can be fixed. This can also be repaired by using artificial processes, especially industrial ones that produce ammonia and fertilizers high in nitrogen.

Nitrogen Fixation Example

In nature, nitric oxide is fixed, or mixed, as nitric oxide by lightning and ultraviolet radiation, but larger quantities of nitrogen are fixed by soil microorganisms as ammonia, nitrites, and nitrates.
They influence more than 90% of all nitrogen fixing. The cyanobacteria (or blue-green algae) Anabaena and Nostoc, as well as genera like Azotobacter, Beijerinckia, and Clostridium, are examples of free-living (nonsymbiotic) bacteria.
Mutualistic (symbiotic) bacteria include Rhizobium, which is linked to leguminous plants, and various Azospirillum species, which are linked to cereal grasses.
The nitrogen-fixing bacteria that live in symbiosis infiltrate the host plants’ root hairs, where they multiply and encourage the growth of root nodules, which are enlargements of plant cells and bacteria that are closely bonded.
The bacteria in the nodules convert free nitrogen to ammonia, which the host plant uses for growth.
Seeds are typically inoculated with commercial cultures of suitable Rhizobium species, especially in soils deficient in or lacking the necessary bacterium, to ensure sufficient nodule formation and optimum growth of legumes (such as alfalfa, beans, clovers, peas, and soybeans).

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Nitrogen Fixation: FAQs

Ques. What is nitrogen fixation process?

Ans. Any natural or artificial process known as nitrogen fixation causes free nitrogen (N2), a relatively inert gas present in large quantities in the atmosphere, to chemically interact with other elements to generate more reactive nitrogen compounds like ammonia, nitrates, or nitrites.

Ques. What is nitrogen fixation with example?

Ans. The symbiotic relationship between the water fern Azolla and the cyanobacterium Anabaena azollae is an illustration of this sort of nitrogen fixation. Cavities created at the base of Azolla fronds are colonised by Anabaena. In specialised cells known as heterocysts, the cyanobacteria fix a sizable amount of nitrogen there.

Ques. What are the 2 types of nitrogen fixation?

Ans. Physical nitrogen fixation and biological nitrogen fixation are the two methods of nitrogen fixation. The most common macro-essential element in living things, after carbon, hydrogen, and oxygen, is nitrogen.

Ques. What is the purpose of nitrogen fixation?

Ans. The purpose of nitrogen-fixing bacteria is to provide plants with a crucial nutrient that they are unable to receive naturally from the air. Microorganisms that fix nitrogen can obtain assimilative N for plants in a way that crops cannot. It is absorbed by bacteria from the atmosphere as a gas and released to the soil, mostly as ammonia.

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