rhizobium

noun

rhi·​zo·​bi·​um rī-ˈzō-bē-əm How to pronounce rhizobium (audio)
plural rhizobia rī-ˈzō-bē-ə How to pronounce rhizobium (audio)
: any of a genus (Rhizobium) of small heterotrophic soil bacteria capable of forming symbiotic nodules on the roots of leguminous plants and of there becoming bacteroids that fix atmospheric nitrogen
rhizobial adjective

Word History

Etymology

New Latin, from rhiz- + Greek bios life — more at quick entry 1

First Known Use

1890, in the meaning defined above

Time Traveler
The first known use of rhizobium was in 1890

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Cite this Entry

“Rhizobium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/rhizobium. Accessed 26 Jul. 2025.

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