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Related to rhizobium: Rhizobium radiobacter, Rhizobium bacteria
n. pl. rhizo·bia (-bē-ə)
Any of various aerobic bacteria of the genus Rhizobium that form root nodules in leguminous plants, such as clover and beans, where they establish a symbiotic relationship in which the bacteria obtain carbon and energy from the plant while supplying the plant with nitrogen by nitrogen fixation.