Note on Application of Microbes in Environment, Environmental Genomics of Cyanobacteria, Microbial Nitrogen Cycle

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Ecological significances of soil microorganism

Soil microorganism is very important as almost every chemical transformation taken place in soil involves the active contribution from soil microorganisms. In particular, they play an active role in the formation -of soil fertility as a result of their involvement in the cycle of nutrients like carbon and nitrogen,which are required for plant growth. For example, Soil microorganism are responsible for the decomposition of the organic matter entering the soil example plant more it and therefore in the recycling of nutrients in the soil. Certain soil microorganism such as mycorrhizal fungi can also increase the availability of mineral nutrients example phosphorus to plants. Other soil microorganisms can increase the amount of nutrients present in the soil. For instance, nitrogen-fixing bacteria can transform nitrogen gas present in the soil atmosphere into a soluble nitrogenous compound that plant roots can utilise for growth. This microorganism, which improves the fertility status of the soil and contributes to the plant growth,have been termed as biofertilizers and are receiving increased attention for use as microbial inoculants in agriculture. Similarly, other soil microorganisms have been found to produce compounds i.e vitamins and hormones that ca improve the plant health and contribute to higher crop yield. These microorganisms are currently studied for possible use as microbial inoculants to improve crop yield.

In contrast to these beneficial soil microorganism, other oil microorganism is pathogenic to plants and may cause considerable damage to the crops. Large numbers of pathogenic microorganism are routinely found in the soil and many can infect the plant through the roots[. However certain native microorganisms present in the soil are antagonistic to these pathogens and can prevent the infection of crop plants. Antagonism against plant pathogens usually involves competition for nutrients and production of inhibitory compounds such as secondary metabolites i.e antimicrobial metabolites and antibiotics and extracellular enzymes. Other soil microorganisms produce compounds that stimulate the natural defence mechanisms of the plant and improve its resistance to pathogens. Collectively, these soil microorganisms have been termed biopesticides and represent an emerging and important alternative i.e biological control to the use of chemical pesticides for the protection of crops against pathogens and pests.


Bacteria actinomycetes and fungi are the important decomposers of the ecosystem. They are also called as reducers. figure: earthworm
figure: earthworm

1: Bacterial decomposers:

Bacillus, Pseudomonas, and Clostridium are the important bacterial decomposers. They decompose the organic matter present in soil that can be utilized by the plants in the form of fertilizers.

2: Actinomycetal decomposers:

The majority of the actinomycetes the good decomposers. Streptomyces is one of the important genera of actinomycetes acting as decomposers.

3: Fungal decomposers:

Agaricus,Mucor, Penicillium etc are the important fungi that act as decomposers. They release hydrolytic enzymes into the substratum and break down the complex organic compound into the simpler ones, releases mineral and make them available to plants for recycling.

Life on the earth would have been impossible without decomposers i.e otherwise nutrient would have locked up in the dead bodies of the organism.

Role of decomposers

1; Scavengers of nature;

They decompose the dead bodies of plants and animals. Examples bacteria are the most important scavenger of nature. They decomposer of dead bodies without any cost.

2: Formation of humus:

They help in the formation of humus. It is important to increase the soil fertility and healthy growth of plants.

3: Role of biogeochemical cycles:

They play an important role in converting complex organic component into simpler ones by continuing important component of biogeochemical cycles.

Biodeterioration of organic compounds

Biodeterioration is the spoilage or damage of organic compound. It is a physical or chemical alteration of a product which decreases the usefulness of the product i.e intended purpose is decreased caused by the microorganism or their enzyme.

1: Biodeterioration of agricultural products:

the attack of microorganism on agricultural products like grains,pulses,meat and other products bring the physical as well as chemical changes sp reduce te nutritional value of food products. The microorganism separated products are poisonous due to the enzymes secreted by the microorganism. Aspergillus species, Penicillium, Trichoderma, Fusarium, Mucor, Bacterial species are responsible for biodeterioration of agricultural products. The organism is Pseudomonas, Clostridium etc.

2: Biodeterioration of pulpwood products and paper:

In paper production, microbial activities are utilized in solubilizing, which instead also cause loss. The microbial attack on paper quality becomes low. Fungi are more responsible for the detonation of paper than bacteria. The fungi species which are responsible for the deterioration

is mucor,penicillin,fusarium,leucoderma and some yeast species. The paper is subjected to deterioration, cellulose is susceptible to fungal deterioration example Aspergillus,Cladosporium

3: Biodeterioration of textiles or fibres:

Mucor is mainly responsible for the damage of cellulose. Fibres genus mesothelium is responsible for the deterioration of cellulose of Fibres . Mucor growth is favoured by high humidity. Moderate temperature and diffused light. The aerobic groups of bacteria can deteriorate fibres because they have cellulose-digesting enzymes.

4: Biodeterioration of paints and painted surface:

the microorganism can deteriorate the paints and painted surface , the degree of deterioration depends on upon the chemical structure of organic material used and the physical and chemical environment. Fungi are mostly responsible for biodeterioration of paints examples Cladosporium,Aurcobasidium.

5: Biodeterioration of other organic materials;

Microorganism like Pseudomonas and Desulphovibrio are mainly responsible for causing deterioration of optical equipment. The plastic products are deteriorated by mucor,penicillium,aspergillus and rhizopus. Microorganism deteriorates problem examples Cladosporium resonate i.e kerosene fungus. Deterioration of the concrete product by Thiobacillus trioxides producing hydrogen sulphate.

why COD values are higher than BOD values???

COD values are higher than BOD values because certain organic substances which are difficult to get oxidized by common microbial oxidants can easily undergo chemical oxidation with strong oxidizing agents quickly.

Techniques used for the estimation of microbial population

Different techniques cab be employed for the estimation of the microbial population but serial dilution method among them is most commonly used one. In serial dilution method, first preparation of serial dilution from 10-1 to 10-10 from sample whether soil or water i.e 1 gram in 100ml is done then it is calculated in the different Petri plate containing nutrient agar at 388-degree centigrade. After 24 hours incubation, a bacterial colony can be counted in number.


Miller, Jr. G.T.Living in the Environment. Wadsworth Publication, 2003.

S.C., Santee.Environmental Science. India, New Center: New Center Book Agency (P) Ltd, 2004.

T., Richard.Environmental Science Towards a Sustainable Future. India: PHI (P) Ltd., 2008.

  • A microorganism that converts gaseous nitrogen to a suitable form that can be used by living beings is very important for life on earth. This type of process is called nitrogen fixation.
  • Symbiotic nitrogen fixation is a coordinator process in which the reside or stay inside the plants and residue atmospheric nitrogen to ammonia. This ammonia then can be utilized or used by the plants for the synthesis of proteins and the other nitrogen containing compounds such as nucleic acids.
  • Algae are a highly diverse group of protest which is ranging from unicellular organism to the complex multicellular organisms with a range of differentiate tissues and distinct organs.
  • Diplomonads are a group of mitochondrion-lacking and binucleated flagellates found in the anaerobic microaerophilic environments.

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