BIOGEOCHEMICAL CYCLES in Environment.pptx

BIOGEOCHEMICAL cycle
* Nitrogen cycle
* Carbon cycle
* Iron cycle
* Sulfur cycle

1. BIOGEOCHEMICAL CYCLE BP231507 SWETHA. S 1 ST M.SC MICROBIOLOGY

2. A biogeochemical cycle is the natural process by which nutrients and elements are passed between the biosphere, lithosphere, hydrosphere and atmosphere. The biogeochemical cycle has five cycles. They are 1. Carbon cycle 2. Nitrogen cycle 3. Iron cycle 4. Sulphur cycle

3. 1 . Carbon cycle Carbon is called as the “ chemical building block of life ” because living organisms are made up of it. Carbon cycle is the process where Carbon compounds are interchanged among the Biosphere, Geosphere, Pedosphere, Hydrosphere, and Atmosphere of the earth. STEPS INVOLVED IN CARBON CYCLE * In general, Carbon cycle has four steps. They are 1) Photosynthesis 2) Decomposition 3) Respiration 4) Combustion

4. 1. PHOTOSYNTHESIS Carbon present in the atmosphere is absorbed by plants for Photosynthesis. Plants pull in Carbon-di-oxide out of the air through photosynthesis. Even though, Carbon-di-oxide makes up less than 1 % of the atmosphere, it plays a major role for living things. With CO2 and H2O in the atmosphere, photosynthesis produces sugars like Glucose. This is the plant material that plants synthesize on its own.

5. 2. DECOMPOSITION Plants are then consumed by animals, and carbon gets bioaccumulated into their bodies. Decomposition is the process of breaking down plants and animals. Over vast periods of time, layers of sediment build on each other. Because of the pressure and heat from within the Earth’s crust, this generates fossil fuels. Anaerobic decomposition involves bacteria breaking down Organic matter such as Glucose into CO2 and Methane (CH4). The nutrient cycle recycles Inorganic and Organic material in soil through the process of Decomposition. Then, it goes back again through the same process again.

6. 3. RESPIRATION Human body also made of Carbon because human consume plants as their major food. Animals rely on plants for food, energy and oxygen. Our cells require Oxygen to break down the food we consume through Cellular respiration. Once consumed, Carbon-di-oxide is released into the atmosphere because of Cellular respiration. In turn, this CO2 produced from respiring cells can be used in Photosynthesis again.

7. 4. COMBUSTION Automobiles use Carbon in the form of Fossil fuel and Carbon is also a pollutant as Carbon di-oxide. The Fossil fuels are then used for man-made activities, which pumps more Carbon back into the atmosphere. Carbon dioxide is one of the Greenhouse gases contributing to climate change.

8. 2. IRON CYCLE Iron (Fe) is one of the most abundant elements in Earth’s crust. The Iron cycle (Fe) is the Biogeochemical cycle of Iron through the Atmosphere, Hydrosphere, Biosphere and Lithosphere. STEPS INVOLVED IN IRON CYCLE * On the surface of earth, Iron exists naturally in Two oxidation states, ( i ) Ferrous [Fe2+ or Fe(II)] and (iii) Ferric [Fe3+ or Fe(III)]. A third oxidation state, Fe0 is abundant in Earth’s core and is also a major product of human activities from the smelting of Iron ores to form Cast iron.

9. Iron cycle has two steps. They are 1) Ferrous iron oxidation 2) Ferric iron reduction Iron cycle (Oxidation – Yellow; Reduction – Red)

10. 1. FERROUS IRON OXIDATION In Ferrous iron oxidation, the Ferric iron (Fe3+) is reduced to the Iron ore (Fe0) and then oxidized to Ferrous iron (Fe2+). This reaction is a Chemical oxidation process. The oxidized Ferrous iron (Fe2+) is again reduced to Iron ore (Fe0). The Ferrous iron (Fe2+) undergoes Ferrous iron oxidation by Bacterial or Chemical oxidation process and results in formation of Ferric iron (Fe3+). Microorganisms involved in Ferrous iron oxidation process are Gallionella sp., Thiobacillus ferrooxidans , Sulfolobus sp., Iron bacteria ( Sphaerotilus sp. & Leptothrix sp.) and Dechlorosoma suillum .

11. 2. FERRIC IRON REDUCTION The oxidized Ferric iron (Fe3+) is reduced to Ferrous iron (Fe2+) by Bacterial or Chemical reduction process. Ferric Iron Reduction is a Two steps process. Step - I : Ferric iron (Fe3+) is reduced to Ferric hydroxide (FeOH3) Step - II : Ferric hydroxide (FeOH3) is reduced to Ferrous iron (Fe2+) Microorganisms involved in Ferric iron reduction process are Geobacter metallireducens , Geobacter sulfurreducens , Ferribacterium limneticum, Shewanella putrefaciens and Aquaspirillum magnetotaticum .

12. 3. NITROGEN CYCLE 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.

13. STEPS INVOLVED IN NITROGEN CYCLE In general, Nitrogen cycle has Five steps. They are 1) Nitrogen fixation 2) Nitrification 3) Assimilation 4) Ammonification 5) Denitrification

14. 1. NITROGEN fixation Nitrogen fixation refers to the conversion of atmospheric Nitrogen gas (N2) into Ammonia (NH4) or related nitrogenous compounds, a form usable by plants and other organisms. In Nitrogen fixation, the N2 is split up into free N2 atoms by breaking the triple bond (N≡N) with the help of an enzyme Nitrogenase. Nitrogen fixation can takes place by two methods. They are 1) Non – Biological or Physical Nitrogen fixation or Natural Nitrogen fixation 2) Biological Nitrogen fixation a) Non – symbiotic or Asymbiotic or Free living Nitrogen fixation b) Symbiotic Nitrogen fixation c) Associative Symbiotic Nitrogen fixation d) Endophytic Nitrogen fixation

15. Microorganisms (particularly Prokaryotes) fix 70 % Nitrogen for requirement of plants. Microorganisms that can fix N2 are called Diazotrophs (both bacteria and archaea). Biological nitrogen fixation occurs when atmospheric Nitrogen is converted to Ammonia by an enzyme called a Nitrogenase. The whole Biological Nitrogen fixation process requires 8 electrons and atleast 16 ATPs.

16. 2. nitrification In Nitrification, a host of soil bacteria participate in turning Ammonia into Nitrate – the form of nitrogen that can be used by plants and animals. Nitrification is the 2 Steps process. In Step 1 , Ammonia is oxidized into Nitrite with the help of bacteria Nitrosomonas sp. ( Nitrosomonas eurospora ) or Nitrococcus sp. or Nitrosolobus sp. The Ammonia oxidizing bacteria are Chemoautotrophs in nature. In Step 2 , Nitrite is oxidized into Nitrate with the help of Nitrobacter sp. Or Nitrospira sp.

17. 3. assimilation In Nitrogen assimilation, plants consume the Nitrates made by 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 then able to use these amino acids and nucleic acids in their own cells.

18. 4. ammonification Ammonification is performed by Soil bacteria which 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 up again by Plants and Nitrifying bacteria. The bacteria helps in Ammonification process are Pseudomonas sp., Bacillus sp., Clostridium sp. and Serratia sp. The fungi helps in Ammonification process are Alternaria sp., Mucor sp., Aspergillus sp. And Penicillium sp.

19. 5. denitrification Denitrification is the final step of Nitrogen cycle. Denitrification is the process that converts Nitrate to Nitrogen gas by Denitrifying bacteria. Denitrification occurs in waterlogged soils, where little oxygen is available. In the absence of oxygen as an electron acceptor, Denitrifying bacteria substitute the Nitrates of agricultural fertilizer. This converts much of the valuable Nitrate into Gaseous nitrogen that enters the atmosphere. Some of the Denitrifying bacteria involved in Denitrification process are Pseudomonas sp., Bacillus sp., Paracoccus denitrificans and Thiobacillus denitrificans .

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