cy·​a·​no·​bac·​te·​ri·​um | \ ˌsī-ə-nō-bak-ˈtir-ē-əm How to pronounce cyanobacterium (audio) , sī-ˌa-nō- \

Definition of cyanobacterium

: any of a major group (Cyanobacteria) of photosynthetic bacteria that are single-celled but often form colonies in the form of filaments, sheets, or spheres and are found in diverse environments (such as salt and fresh water, soils, and on rocks)

Note: Like other bacteria, cyanobacteria lack a nuclear membrane and membrane-bound organelles and have cell walls containing peptidoglycan. However, cyanobacteria were more commonly grouped with algae in the past because they possess a type of chlorophyll (chlorophyll a) not found in other bacteria and because they produce oxygen as a by-product of photosynthesis.

called also blue-green alga

Other Words from cyanobacterium

cyanobacterial \ ˌsī-​ə-​nō-​bak-​ˈtir-​ē-​əl How to pronounce cyanobacterium (audio) , sī-​ˌa-​nō-​ \ adjective

Examples of cyanobacterium in a Sentence

Recent Examples on the Web Lichens are actually two organisms working together: a fungus and either alga or cyanobacterium. Corryn Wetzel, Smithsonian Magazine, 17 Feb. 2022 One day, another organism—a sort of proto-alga—devoured a cyanobacterium. Elizabeth Kolbert, The New Yorker, 6 Dec. 2021 Called Chroococcidiopsis, this cyanobacterium has a reputation for survival so formidable it is being considered for terraforming Mars. Jennifer Frazer, Scientific American, 4 Mar. 2021 The cyanobacterium was a new species, which Wilde named Aetokthonos hydrillicola in 2014. Erik Stokstad, Science | AAAS, 25 Mar. 2021 In a fateful encounter, a cyanobacterium was engulfed by a eukaryote, a cell that had evolved the capacity for internal organs, and lived on within its membrane. Lucy Jakub, The New York Review of Books, 1 Dec. 2020 His team used a type of cyanobacterium from the genus Synechococcus. Sophie Bushwick, Scientific American, 15 Jan. 2020 Polluted Midwest floodwaters have fed an outbreak of cyanobacterium. Washington Post, 15 July 2019 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'cyanobacterium.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of cyanobacterium

1974, in the meaning defined above

History and Etymology for cyanobacterium

New Latin

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Time Traveler for cyanobacterium

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The first known use of cyanobacterium was in 1974

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Dictionary Entries Near cyanobacterium

cyanoauric acid



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Cite this Entry

“Cyanobacterium.” Dictionary, Merriam-Webster, Accessed 13 Aug. 2022.

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More Definitions for cyanobacterium


cy·​a·​no·​bac·​te·​ri·​um | \ -bak-ˈtir-ē-əm How to pronounce cyanobacterium (audio) \
plural cyanobacteria\ -​ē-​ə \

Medical Definition of cyanobacterium

: any of a major group (Cyanobacteria) of photosynthetic bacteria that produce molecular oxygen and use water as an electron-donating substrate in photosynthesis

called also blue-green alga


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