Ammonification – Definition, Stages and Examples – UPSC Environment Notes

When an organism expels waste or undergoes death, the nitrogen within its tissues exists in the form of organic nitrogen (e.g., amino acids, DNA). Subsequently, a range of fungi and prokaryotes decompose the tissue, releasing inorganic nitrogen back into the ecosystem as ammonia through the Ammonification process.

One of the vital components crucial for the sustenance of all living organisms is nitrogen. It plays a fundamental role in the creation of numerous biomolecules, including proteins, DNA, and chlorophyll. Despite its abundance in the atmosphere as dinitrogen gas, accessibility to most species is restricted in this form, turning it into a limited resource that frequently constrains primary productivity in various ecosystems.

Nitrogen becomes readily available to primary producers, such as plants, only after its transformation from dinitrogen gas to ammonia.

Nitrogen exists in diverse inorganic and organic forms, extending beyond dinitrogen and ammonia. As organisms utilize nitrogen for growth and, in specific instances, energy, it undergoes distinct changes within the environment. Nitrogen undergoes transformations primarily through processes like nitrogen fixation, nitrification, denitrification, ammonium production, and anammox. The biosphere’s productivity is significantly reliant on the oxidation of nitrogen into its various oxidation states, a task carried out by a broad spectrum of microorganisms.


The nitrogen cycle encompasses the crucial process of ammonification, providing organisms with the essential nitrogen necessary for their survival. Ammonification involves microscopic organisms, such as bacteria or decaying creatures, converting nitrogen-containing compounds from deceased organic matter into simpler molecules like ammonia. These simplified materials play a vital role in supporting the ecology.

What Do Bacteria Do During Ammonification?

When a living organism expires, it releases nitrogen from its cells or tissues in the form of organic nitrogen, comprising substances like amino acids and DNA. Microbes, including fungi and prokaryotes, work collectively to decompose the tissue and convert organic nitrogen into its inorganic form. Each bacterium utilizes this inorganic nitrogen.

Steps involved in Ammonification

  • In the ammonification process, NH3 groups undergo conversion to (NH4+), resulting in ammonia.
  • Substrates for ammonification include urea, uric acid, and organic nitrogen from feces.
  • Ammonia is further processed, combining to produce a variety of amino acids, essential for various metabolic processes.
  • Living organisms encompass molecules containing nitrogen, such as proteins, nucleic acids, DNA, vitamins, urea, and others.

Implications of Ammonification

  • Organic nitrogen undergoes transformation into inorganic ammonia or ammonium ions through the ammonification process.
  • Nitrogen within compounds in living organisms is typically in the form of organic nitrogen.
  • Ions, proteins, vitamin B, urea, and other chemicals represent examples of nitrogen-containing substances in living entities.
  • Nitrogen is present in waste products and the remains of deceased plants or animals used in the process of ammonification.
  • The environment needs nitrogen accessible to living organisms. Ammonification is crucial in this context, as it contributes nitrogen to the soil in a form usable by plants and transferable through the food chain.
  • Ammonification serves as an essential method for obtaining nitrogen, particularly for many plant species thriving in acidic soils.
  • The introduction of fertilizers to increase ammonia levels in the soil may lead to the overgrowth of algae, resulting in soil toxicity and an imbalance in the ecosystem.

Examples of ammonification

Examples of ammonifying bacteria include Bacillus, Proteus, Clostridium, Pseudomonas, and Streptomyces.


Another pivotal phase in the global nitrogen cycle is nitrification, a process that converts ammonia into nitrite and ultimately nitrate. This transformation is predominantly carried out aerobically, exclusively by prokaryotes. Two distinct stages of nitrification are executed by different microorganisms. The first step, involving the oxidation of ammonia to nitrite, is performed by ammonia-oxidizing bacteria.

Aerobic ammonia oxidizers rely on two crucial enzymes, ammonia monooxygenase and hydroxylamine oxidoreductase, to facilitate the conversion of ammonia to nitrite through the intermediary hydroxylamine. Despite being recognized for their exceedingly slow growth due to the minimal energy produced compared to other metabolic processes, these ammonia oxidizers are noteworthy. Similar to photosynthetic organisms, they are autotrophs, utilizing carbon dioxide to generate organic carbon while employing ammonia as their energy source instead of light.

While ammonia oxidation is less prevalent among prokaryotes compared to nitrogen fixation, which involves a diverse range of microorganisms, it was initially believed that only a small number of bacterial species were responsible for all ammonia oxidation. Currently, our understanding of the physiological diversity of ammonia-oxidizing archaeons is limited, as only one has been cultivated in pure culture.

The second stage of nitrification involves the conversion of nitrite to nitrate, and this is carried out by a distinct group of prokaryotes known as nitrite-oxidizing bacteria. Similar to ammonia oxidizers, nitrite oxidizers exhibit extremely low growth yields due to the limited energy produced through nitrite to nitrate oxidation. In fact, numerous ammonia or nitrite molecules must undergo oxidation before an ammonia or nitrite oxidizer can fix a single carbon dioxide molecule.

In aerobic conditions, both nitrite- and ammonia-oxidizers are prevalent and have been extensively studied in various natural settings, including soils, estuaries, lakes, and open oceans. Notably, in wastewater treatment plants, ammonia- and nitrite-oxidizers play a critical role by removing potentially harmful quantities of ammonium, preventing the contamination of receiving waters.


In summary, the nitrification process is a crucial link in the global nitrogen cycle, facilitated by prokaryotes, specifically ammonia-oxidizing bacteria and nitrite-oxidizing bacteria. The complex biological mechanism transforms ammonia into nitrate, contributing to essential ecological processes. Despite slow growth, the physiological diversity of ammonia-oxidizing archaeons remains poorly understood, necessitating further research. These nitrogen-transforming microorganisms thrive in diverse environments, impacting ecosystems from soils to oceans. In wastewater treatment plants, they play a vital role in safeguarding water quality by mitigating ammonium contamination. Their intricate interplay underscores their importance in maintaining nitrogen cycling balance in natural and engineered systems. Ongoing exploration promises enhanced comprehension for potential applications in environmental management and sustainability.

FAQs on Ammonification

Question 1: What is the purpose of nitrogen tanks?

Answer: Nitrogen tanks are used to prevent oxidation and establish a secure, inert atmosphere, eliminating gases produced by furnaces.

Question 2: How is nitrogen fixed?

Answer: Nitrogen is biologically fixed in the soil by diazotrophs, including bacteria like Azotobacter and archaea. Symbiotic relationships with nitrogen-fixing bacteria are particularly common in legumes.

Question 3: How does nitrogen exist in the environment?

Answer: The majority of nitrogen molecules are present in the atmosphere. In both soil and water, nitrogen exists in the forms of nitrates and nitrites.

Question 4: Define denitrification.

Answer: Denitrification is the process where nitrogen compounds, specifically nitrate, are converted into gaseous nitrogen, releasing them back into the atmosphere. This occurs in the penultimate stage of the nitrogen cycle without oxygen.

Question 5: What are the products of ammonification?

Answer: The products of ammonification are ammonia and ammonium ions.

Question 6: When does ammonification occur?

Answer: Ammonification occurs during the process of nitrogen fixation.

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