Biogeo chemical cycle...(Nitrogen cycle)

It may also be considered as the movement of nitrogen through the food chain from simple inorganic
compounds, mainly ammonia, to complex organic compounds.
 This complex cycle involves bacteria, plants, and animals.
 All organisms can convert ammonia (NH3) to organic nitrogen compounds that are compounds
containing C–N bonds. However, only a few microorganisms can synthesize ammonia from nitrogen
gas (N2).
 Although N2 gas makes up about 80% of the earth’s atmosphere, it is a chemically unreactive
compound and thus needs to be changed in order to be utilized by living beings.
 Within the biosphere, there is a balance between total inorganic and total organic forms of nitrogen.
 The conversion of organic to inorganic nitrogen comes about through catabolism, de-nitrification, and
decay.
 Nitrogen is the most abundant element in the atmosphere. Although, 78 % volume of the atmosphere
is Nitrogen gas.
 Nitrogen is essential to life because it is a key component of proteins and nucleic acids.
 The Nitrogen cycle refers to the cycle of nitrogen atoms through the living and non-living systems of
Earth.

1. NITROGEN CYCLE B. LOKESHWARI II M. Sc MICROBIOLOGY SACRED HEART COLLEGE (AUTONOMOUS) TIRUPATTUR.

2. INTRODUCTION Complex cycle involves bacteria, plants, and animals . Converts ammonia (NH3) to organic nitrogen compounds containing C–N bonds. They can synthesize ammonia from nitrogen gas (N2 ). N2 gas makes up about 80% of the earth’s atmosphere. C onversion of organic to inorganic nitrogen comes about through catabolism, de-nitrification, and decay. Essential to life and key component of proteins and nucleic acids.

3. STEPS INVOLVED – 5 STEPS

4. 1. NITROGEN FIXATION Conversion of atmospheric Nitrogen gas (N2) into Ammonia (NH4) or related nitrogenous compounds N2 is split up into free N2 atoms by breaking the triple bond (N≡N) Nitrogen fixation can takes place by two methods ;

5. Microorganisms fix 70 % Nitrogen for requirement of plants. Microorganisms that fix N2 are called Diazotrophs . The overall reaction for Biological nitrogen fixation (BNF) Requires 8 electrons and atleast 16 ATPs. The ability to reduce atmosphere Nitrogen is restricted only to bacteria Rhizobia are the first group of organism realized for its potential of nitrogen fixation

6. 2. NITRIFICATION Soil bacteria turns the Ammonia into Nitrate Nitrification is the 2 Steps process .

7. 3 . ASSIMILATION In Nitrogen assimilation, plants consume the Nitrates from soil bacteria through its roots and use them to make Nucleotides, amino acids, plant proteins and other vital chemicals for life. Animals that eat the plants are able to produce these amino acids and nucleic acids in their own cells .

8. 4. AMMONIFICATION Ammonification is performed by Soil bacteria that decompose dead plants and animals. During the Ammonification process, these decomposers break down Amino acids and Nucleic acids into Nitrates and Ammonia and release those compounds back into the soil. The Ammonia produced may be taken again by Plants and Nitrifying bacteria. Bacteria - Pseudomonas sp., Bacillus sp., Clostridium sp. and Serratia sp . Fungi - Alternaria sp., Mucor sp., Aspergillus sp. and Penicillium sp

9. 5.D ENITRIFICATION Final step of Nitrogen cycle. Converts Nitrate to Nitrogen gas by Denitrifying bacteria. Denitrification occurs in waterlogged soils. In the absence of oxygen as an electron acceptor, Denitrifying bacteria substitute the Nitrates of agricultural fertilizer and converts the valuable Nitrate into Gaseous nitrogen that enters the atmosphere Denitrifying bacteria - Pseudomonas sp., Bacillus sp ., Paracoccus denitrificans and Thiobacillus denitrificans .

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