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

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Other Words from cyanobacterium

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

Examples of cyanobacterium in a Sentence

Recent Examples on the Web

Polluted Midwest floodwaters have fed an outbreak of cyanobacterium. Washington Post, "The Latest: Toxic bacteria keep Mississippi beaches closed," 15 July 2019

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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Statistics for cyanobacterium

Last Updated

6 Aug 2019

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Time Traveler for cyanobacterium

The first known use of cyanobacterium was in 1974

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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

Comments on cyanobacterium

What made you want to look up cyanobacterium? Please tell us where you read or heard it (including the quote, if possible).


one from the Upper Peninsula of Michigan

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