Bacteria, nitrogen-fixation processes

A class of plants, called legumes, has bacteria which extract N2 directly, converting it to NH3. This nitrogen fixation process, catalyzed by an enzyme produced by the bacteria, is highly efficient at usual temperatures and pressures. 

Ineffectiveness often involves cross-inoculation groups strains of bacteria that produce effective nodules on some plant species may produce ineffective nodules on other species. A single plant may be infected with both good and bad strains and in this case the poor strains may act as partial inhibitors of nitrogen fixation. Ineffective nodules usually develop little or no bacteroid tissue, and the growth of the meristematic tissue at the tip of the nodule may be markedly curtailed. The most distinctive feature of ineffectiveness is the absence of hemoglobin which is believed to play an important part in the biochemical nitrogen fixation process. 

Nitrogen fixation Conversion of atmospheric nitrogen into organic nitrogen compounds available to green plants a process that can be carried out only by certain strains of soil bacteria. 

Besides nitrogen fixation, the only other major source of reduced nitrogen is the decomposition of soil or aquatic organic matter. This process is called ammonification. Heterotrophic bacteria are principally responsible for this. These organisms utilize organic compounds from dead plant or animal matter as a carbon source, and leave behind NH3 and NHJ, which can then be recycled by the biosphere. In some instances heterotrophic bacteria may incorporate a complete organic molecule into their own biomass. The majority of the NH3 produced in this way stays within the biosphere however, a small portion of it will be volatilized. In addition to this source, the breakdown of animal excreta also contributes to atmospheric... 

Nevertheless, cereal plants can interact with endosymbionts, capable of nitrogen fixation in other species, and be stimulated in their productivity. The odds of soil life are balanced for some bacteria by their interactivity at rhizosphere level, and a realm of exchanged signals dictates entry into hormonally reprogrammed root sites. Specificity for partner plant species is part of a fine speciation process that actively involves the bacterial nodulation genes, and continues to drive their variation dynamics. 

Nitrogen fixation The process by which some bacteria and phytoplankton are able to convert Nj into organic nitrogen. The energy required is large because a triple bond must be broken. 

A large number of ferredoxin-dependent enzymes have been identified in bacteria . Flavodoxin will replace ferredoxin in most of these. Among the biochemical processes in which these proteins function are nitrogen fixation, hydrogen production and sulfate reduction. 

Ammonia is oxidized in nature to nitrate via several intermediates in the process of nitrification. Nitrate may be reduced to nitrite by either a dissimilatory or an assimilatory process. Nitrite may be assimilated into the cell via reduction to ammonia, or it may be reduced by microorganisms to N20 and N2 in denitrification. A major part of the total nitrogen in this pathway is lost to the atmosphere. However, in turn, atmospheric dinitrogen is converted to ammonia by various bacteria in nitrogen fixation. 

Nitrogen fixation is the conversion of N2 gas into ammonia, a process carried out by some soil bacteria, cyanobacteria and the symbiotic bacteria Rhizobium that invade the root nodules of leguminous plants. This process is carried out by the nitrogenase complex, which consists of a reductase and an iron-molybdenum-containing nitrogenase. At least 16 ATP molecules are hydrolyzed to form two molecules of ammonia. Leghemoglobin is used to protect the nitrogenase in the Rhizobium from inactivation by 02. 

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