Cycles of Elements

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Soil Microbiology Nature of Soil Soil Habitats (Lithosphere) Microorganisms in Soil Decomposition of Organic Matter in Soil Bacteria in Soil Physiological Types of Bacteria in Different Soils Fungi in Soil Protozoa in Soil Algae in Soil Viruses in Soil Functions of Microorganisms in Soil Humus Functions of Humus Cycles of Elements Carbon Cycle Nitrogen Cycle

Cycles of Elements

	Cycles of Elements - Elements which are essential components of the protoplasm undergo cyclic alterations between an inorganic state, free in nature, and a combined state in living organisms. This repeated transformation pi elements from living protoplasm to the free state in nature constitutes the cycles of elements. When plants and other soil organisms die, their organic constituents are mineralized by microorganisms.
Mineralization of organic carbon, nitrogen, sulphur and phosphorus by soil microorganisms makes these elements available for reuse. When these, elements except phosphorus) are incorporated into the protoplasm, there is usually a change in their oxidation state. The elements are generally found in a reduced state in the protoplasm. However, when mineralized, they are in an oxidized state. The elements, therefore, serve three functions.
1) As essential constituents of protoplasm. 2) As sources of energy oxidation (for chemolithotrophs) and 3) As electron acceptors in oxidation reactions.

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Sulphur Cycle Ammonification in Soil Nitrification in Soil Nitrate Reduction in Soil Denitrification in Soil Nitrogen Fixation Symbiotic Nitrogen Fixation Rhizobium Specificity of Bacteria and Legumes Non-Symbiotic Nitrogen Fixation Non-symbiotic Nitrogen Fixing Microorganisms Mechanism of Nitrogen Fixation Oxidation of Sulphur and Sulphur Compounds by Bacteria