Nitrifying Bacterium


What is a Nitrifying Bacterium?

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The nitrifying bacteria name is the plural of the nitrifying bacterium. They are a small group of aerobic bacteria from the family named Nitrobacteraceae which uses inorganic chemicals as the source of energy. Nitrifying bacteria are microorganisms that play a very vital role in the nitrogen cycle as converters of soil ammonia to nitrates.  

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The process of nitrification, involves two different groups of bacteria, one that converts ammonia to nitrites (Nitrosomonas, Nitrosospira, Nitrosococcus, and Nitrosolobus)  and the other to convert nitrites to nitrates (Bacteria Nitrobacter, Nitrospina, and Nitrococcus). In the process of agriculture, irrigation if the solution is diluted with ammonia results in an increase in the soil nitrates, through the action of nitrifying bacteria.  

Nitrogen Cycle

It is a biogeochemical process, in which nitrogen is converted into different forms. It is a continuous process of passing nitrogen from the atmosphere to the soil and later to the organisms and then back into the atmosphere. The nitrogen process involves several processes like nitrogen fixation, nitrification, denitrification, decay, and putrefaction. 

Nitrogen gas exists in two forms organic and inorganic, in which organic nitrogen exists in the living organisms, which gets passed to the other living organisms through the food chain. The inorganic form of nitrogen is found in the atmosphere in abundance, which is available to plants by symbiotic bacteria that can be converted into inert nitrogen into a usable form like nitrites and nitrates.  

To maintain balance in the ecosystem nitrogen undergoes various types of transformations and furthermore, this process extends to various biomes, with the marine cycle being one of the most biogeochemical cycles. 

Stages of Nitrogen Cycle

The different stages of the nitrogen cycles are – Nitrogen fixation, Nitrification, Assimilation, Ammonification, and Denitrification, these are discussed in detail below. 

Nitrogen Fixation

This is the initial step of the nitrogen cycle, in this process atmospheric nitrogen which is in inert form is converted into ammonia usable form. 

The nitrogen gas is present in the inert form and it is deposited into the soil from the atmosphere and surface waters during this process, through precipitation. In this process, it undergoes a set of changes, where nitrogen atoms will get separated and combine with hydrogen to form ammonia.   

The nitrogen fixation is entirely completed by symbiotic bacteria which are known as Diazotrophs. Azotobacter and Rhizobium also have a major role in this process, as these bacteria consist of a nitrogenase enzyme that has the capability to combine gaseous nitrogen with hydrogen to form ammonia.

Nitrogen fixation can occur through atmospheric fixation which involves lightening or industrial fixation by manufacturing ammonia under high temperature and pressure conditions. Nitrogen can also be fixed by man-made processes, primarily industrial processes that create ammonia and nitrogen-rich fertilizers.

Types of Nitrogen Fixation:

  1. Atmospheric Fixation: It is a natural phenomenon where the energy of lightning breaks the nitrogen into nitrogen oxides and is then used by plants.

  2. Industrial Nitrogen Fixation: This is a man-made alternative that helps in nitrogen fixation by the use of ammonia, it is produced by the direct combination of nitrogen and hydrogen.

  3. Biological Nitrogen Fixation: As the nitrogen is not directly usable from the air to plants and animals. Some of the bacterias such as Rhizobium and blue-green algae transform the unusable form of nitrogen into other compounds that are more readily usable. 


In the process of bacteria nitrification, ammonia is converted into nitrate with the presence of bacteria in the soil, nitrites are formed by the oxidation of ammonia with the help of Nitrosomonas bacteria species. further, the produced nitrites are converted into nitrates with the help of Nitrobacter bacteria, this conversion is very important as ammonia gas is very toxic for plants.  

The process of bacteria nitrification involves the following reaction:

2NH4+ + 3O 2NO2- + 4H+ + 2H2O

2NO2- + O22NO3-


Some of the primary producers like plants take nitrogen compounds directly from the soil, with the help of their roots. which are available in the form of ammonia, nitrite ions, nitrate ions, or ammonia ions, and they are used in the formation of the plant proteins, in this way they enter the food web when the primary consumer eat the plants. 


The nitrogen which is present in the organic matter is released back into the soil, the plants and animals die. some of the decomposers like bacteria and fungi (present in the soil), convert the organism matter back into ammonium. The ammonia produced in this process of decomposition is further used for other biological processes. 


Denitrification is the process by which nitrogen compounds make their way back into the atmosphere by converting nitrate into gaseous nitrogen. This process is the final stage of the nitrogen cycle, which occurs in the absence of oxygen. This process is carried out by the denitrifying bacteria, some of them are Clostridium and Pseudomonas, which will process nitrate to gain oxygen and give out free nitrogen gas as a byproduct.

Difference Between Nitrifying and Denitrifying Bacteria

Nitrifying Bacteria 

Denitrifying Bacteria 

They convert the soil ammonia into nitrates, which are further used by plants. As nitrifying bacteria name signifies the conversion of ammonia into nitrites or nitrates. 

These are the bacterias that break down the nitrated and return nitrogen to the air.

Examples of nitrifying bacteria are Nitrosomonas, Nitrobacter, Nitrospira, Nitrosococcus. 

Examples of denitrifying bacteria are Paracoccus, Rhodobacter, Thauera, and Acidovorax. 

Do You Know?

What would happen to the ecosystem without nitrifying bacteria? The condition of the ecosystem will be worse, as there will be no nitrogen fixation, most of the photosynthesis process will come to a grinding halt within a year. Also, there will be no microbes to break a large amount of waste accumulated. 

FAQ (Frequently Asked Questions)

1. Are Nitrifying Bacteria Chemoautotrophs?

Answer. Yes, Nitrifying bacterias are chemoautotrophs as they use carbon dioxide, carbon for the source of growth, as nitrifying organisms are chemoautotrophs and use carbon dioxide as their carbon source for growth. Chemoautotrophs are the cells that create their own energy from the inorganic chemicals and nitrogen is a chemical on which nitrifying bacteria are completely dependent on their nutritional needs.

2. How Much Time Does it Take to Grow Nitrifying Bacteria?

Answer. Usually, nitrifying bacteria takes 2-6 weeks, at the temperature of 70 Fahrenheit to grow. Nitrifying bacteria grow slowly in comparison to the other type of bacteria, when optimum conditions are maintained it takes complete 15 hours for a colony to double in size.