what are the condition necessary for the rhizobium bacteria to fix nitrogen fixation

The Gram negative soil bacteria, Rhizobium, form root nodules in most leguminous plants. These bacteria in the root nodules help in fixation of atmospheric nitrogen and help in plant growth. The conditions required are as follows:
1. The carbon requirement of the bacteria is taken care of by the host plant.
2. The nitrogen fixing bacteria must stay close to the roots within a region called the rhizosphere.
3. The soil must contain sufficient organic matter for use by the bacteria to fix nitrogen.
4. The roots must show positive chemotaxis to attract Rhizobia. This can be done using flavonoids.
5. The presence of oxygen must be regulated as the nitrogenase enzyme is sensitive to oxygen, and both the Fe protein and the MoFe protein are rapidly and irreversibly inactivated by oxygen.
6. The presence of oxygen-binding protein leghemoglobin to protect nitrogenase enzyme.
7. The enzymes required are nirogenase and hydrogenase.
8. The presence of a non-heme iron protein-ferredoxin as an electron carrier.
9. The presence of hydrogen donating system, constant supply of ATP, thiamine pyrophosphate, coenzyme A, inorganic phosphate and Mg2+ as cofactors.
10. The presence of metal ions cobalt and molybdenum.

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