MAJOR MICROBIAL NITROGEN
MECHANISM OF NITROGEN CYCLE BY ENZYME
ROLE OF ELECTRON IN NITROGEN CYCLE
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.
Atmospheric nitrogen by nitrogen fixing bacteria to yield
N2+8H =NH3+H2 ( Cynobacteria)
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)
= NO3- ( Nitrobactor)
The conversion of nitrate to nitrogen under anaerobic
condition is known as denitrification.
NO3- = N2 (Bacillus, Prococus, pseudomonas)
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
Ammonia Is released during the decomposition of organic
nitrogen compound such as amino acids and nucleotides a
process called ammonification.
Organic N2 =NH4+
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.
Chlorosis appears in older leaves.
Dormancy of lateral buds .
Delaying of flowering .
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.
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
Brock 8th edition . Nitrogen cycle.page 532
Lehninger fourth edition.nitrogen cycle page no. 834