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Rhizobium is a genus of Gram-negative soil bacteria that fix nitrogen. Rhizobium species form an endosymbiotic nitrogen-fixing association with roots of (primarily) legumes and other flowering plants. The bacteria colonize plant cells to form root nodules, where they convert atmospheric nitrogen into ammonia using the enzyme nitrogenase.
The supply of nitrogen through fertilizers has severe environmental concerns. Specific strains of rhizobia are required to make functional nodules on the roots able to fix the N 2. [9] Having this specific rhizobia present is beneficial to the legume, as the N 2 fixation can increase crop yield. [10] Inoculation with rhizobia tends to increase ...
Nitrogen fixation is a chemical process by which molecular dinitrogen (N 2) ... is unusually able to interact with rhizobia and form nitrogen-fixing nodules. [62]
Nitrogen is the most commonly limiting nutrient in plants. Legumes use nitrogen fixing bacteria, specifically symbiotic rhizobia bacteria, within their root nodules to counter the limitation. Rhizobia bacteria convert nitrogen gas (N 2) to ammonia (NH 3) in a process called nitrogen fixation.
Rhizobacteria, through nitrogen fixation, are able to convert gaseous nitrogen (N 2) to ammonia (NH 3) making it an available nutrient to the host plant which can support and enhance plant growth. The host plant provides the bacteria with amino acids so they do not need to assimilate ammonia. [ 5 ]
Bradyrhizobium and other rhizobia take atmospheric nitrogen and fix it into ammonia (NH 3) or ammonium (NH 4 +). Plants cannot use atmospheric nitrogen; they must use a combined or fixed form of the element. After photosynthesis, nitrogen fixation (or uptake) is the most important process for the growth and development of plants. [12]
Nod factors (nodulation factors or NF), are signaling molecules produced by soil bacteria known as rhizobia in response to flavonoid exudation from plants under nitrogen limited conditions. Nod factors initiate the establishment of a symbiotic relationship between legumes and rhizobia by inducing nodulation.
Rhizobium: Symbiotic nitrogen fixation by Rhizobium with legumes contributes substantially to total nitrogen fixation. Rhizobium inoculation is a well-known agronomic practice to ensure adequate nitrogen. [5] [6] One of the most widespread species is R. leguminosarum. Bradyrhizobium spp. (in particular Bradyrhizobium japonicum). [7]