NITROGEN CYCLE

1. NITROGEN CYCLE
PANKAJ
Microbiology

2. CONTENTS
INTRODUCTION
MAJOR MICROBIAL NITROGEN
TRANSFORMATION
MECHANISM OF NITROGEN CYCLE BY ENZYME
ROLE OF ELECTRON IN NITROGEN CYCLE
Nif GENES
DEFIENCY SYMPTOMS

3. INTRODUCTION
The nitrogen cycle is the process by which nitrogen is
converted between its various chemical forms. This
transformation can be carried out via both biological
and non-biological processes. Important processes in
the nitrogen cycle include fixation, mineralization,
nitrification, and denitrification. The majority of
Earth's atmosphere (approximately 78%) is nitrogen.

4. MAJOR MICROBIAL N2
TRANSFORMATION
Nitrogen fixation
Nitrification
Denitrification
Anammox
Ammonification

5. NITROGEN FIXATION
Atmospheric nitrogen by nitrogen fixing bacteria to yield
ammonia.
N2+8H =NH3+H2 ( Cynobacteria)

6. NITRIFICATION
The atmospheric nitrogen is fixed by nitrogen fixing
bacteria to yield ammonia. This ammonia is used by
living microorganism and converted into nitrate.
 NH4+ = NO2- ( Nitrosomonas)
NO2-
= NO3- ( Nitrobactor)

7. Denitrification
The conversion of nitrate to nitrogen under anaerobic
condition is known as denitrification.
NO3- = N2 (Bacillus, Prococus, pseudomonas)

8. ANAMMOX
In this biological process, nitrite and ammonium are
converted directly into dinitrogen gas. This process
contributes up to 50% of the dinitrogen gas produced
in the oceans. It is thus a major sink for fixed nitrogen
and so limits oceanic primary productivity. The
overall catabolic reaction is:
NH4+ + NO2− → N2 + 2H2O. (Brocadia)
The bacteria that perform the anammox process
belong to the bacterial phylum planctomycetes of
which Planctomyces and Pirellula are the best known
genera.

9. AMMONIFICATION
Ammonia Is released during the decomposition of organic
nitrogen compound such as amino acids and nucleotides a
process called ammonification.
Organic N2 =NH4+
( Rhizobium)

12. Nitrogenase complex
1. Dinitrogenase reductase
2. Dinitrogenase

16. Nif Genes
The nif gene is the gene responsible for the coding of
proteins related and associated with the fixation of
atmospheric nitrogen into a form of nitrogen
available to plants. These genes are found in nitrogen
fixing bacteria and cyanobacteria.

17. DEFICIENCY SYMPTOMS
Chlorosis appears in older leaves.
Dormancy of lateral buds .
Delaying of flowering .

18. Reference
Burford, J.R., and J.M. Bremner. 1975. Relationships between
the denitrification capacities of soils and total, water-soluble
and readily decomposable soil organic matter. Soil Biochem.
7:389-394
Marschner, H. 1995. Mineral Nutrition in Higher Plants.
Academic Press, London.
Tisdale, S.L., W.L. Nelson, J.D. Beaton, and J.L. Havlin. 1993.
Soil Fertility and Fertilizers. MacMillan Publishing Co., New
York, N.Y.
Brock 8th edition . Nitrogen cycle.page 532
Lehninger fourth edition.nitrogen cycle page no. 834

19. Thank You