Rhizobium is a bacterium found in soil that helps in fixing nitrogen in leguminous plants. It attaches to the roots of the leguminous plant and produces nodules. These nodules fix atmospheric nitrogen and convert it into ammonia that can be used by the plant for its growth and development.
Rhizobium and leguminous plants live in a symbiotic association with each other. In this, both the organisms are benefited from each other. The bacteria fix atmospheric nitrogen and make it available to the plants. On the other hand, Rhizobium receives nutrition from the plant in the form of organic acids.