Summary notes – The two step process and converted soil bacteria and bacterium PDF

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Summary notes – The two step process and converted soil bacteria and bacterium Procedure from simple inorganic compounds, mainly ammonia, to complex organic compounds. This complex cycle involves bacteria, plants, and animals. All organisms can convert ammonia (NH3) to organic nitrogen compounds that are compounds containing C–N bonds. However, only a few microorganisms can synthesize ammonia from nitrogen gas (N2). Although N2 gas makes up about 80% of the earth’s atmosphere, it is a chemically unreactive compound and thus needs to be changed in order to be utilized by living beings. Within the biosphere, there is a balance between total inorganic and total organic forms of nitrogen. The conversion of organic to inorganic nitrogen comes about through catabolism, denitrification, and decay. Nitrogen Cycle Image Source: BioNinja. Steps of Nitrogen Cycle

1. Nitrogen Fixation The first stage in the nitrogen cycle is the reduction of N2 gas to ammonia, a process called nitrogen fixation. The process of converting atmospheric N2 gas into ammonia is carried out by only a few microorganisms, termed diazotrophs which have an enzyme called “nitrogenase” that combines nitrogen atoms with hydrogen atoms. These are some free-living soil bacteria such as Klebsiella and Azotobacter, cyanobacteria (bluegreen algae), and the symbiotic bacteria (mainly Rhizobium). The amount of N2 fixed by these diazatrophic microorganisms has been estimated to be in the order of 1011 kg per year, about 60% of the earth’s newly fixed nitrogen. Lightning and ultraviolet radiation fix another 15%, with the remainder coming from industrial processes. Ammonia can also be obtained by the reduction of the nitrate ion (NO3–) that is present in the

Principle 2. Nitrification Nitrification is a two-step process in which NH3/ NH4+ is converted to NO3– . First, the soil bacteria Nitrosomonasand Nitrococcus convert NH3 to NO2–, and then another soil bacterium, Nitrobacter, oxidizes NO2– to NO3–. These bacteria are “chemotrophs” who obtain their energy from volatile chemicals. They gain energy through these conversions, both of which require oxygen to occur.

soil. Nitrate reduction can be carried out by most plants and microorganisms. The ammonia resulting from these two processes can then be assimilated by all organisms. Reaction: N2 + 3 H2 –>...