Main Entry: rhi·zo·bi·um

Pronunciation: \rī-ˈzō-bē-əm\

Function: noun

1 capitalized : a genus (family Rhizobiaceae) of small heterotrophic soil bacteria capable of forming symbiotic nodules on the roots of leguminous plants where they fix atmospheric nitrogen
2 plural -bia \-bē-ə\ : any bacterium of the genus Rhizobium