cyanobacterium
noun
cy·a·no·bac·te·ri·um
ˌsī-ə-nō-bak-ˈtir-ē-əm 
sī-ˌa-nō-
: 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
Examples of cyanobacterium in a Sentence
Recent Examples on the Web
At some point, in a sequel to mitochondrial capture, a eukaryote engulfed a cyanobacterium capable of photosynthesis — the process of using sunlight to harvest carbon from the air and spin it into energy.
—
Quanta Magazine, 28 Oct. 2024
In 2024, his lab reported a nitrogen-providing cyanobacterium that had become an organelle within an algal cell.
—Quanta Magazine, 17 July 2024
The algae engulfed a cyanobacterium gives it a bit of a plant superpower.
—Laura Baisas, Popular Science, 18 Apr. 2024
Nostoc commune, also referred to as star jelly, witch's butter and mare's eggs, is a species of cyanobacterium that grows in countries all over the world.
—Victoria Moorwood, USA TODAY, 15 Apr. 2023
Here's what to know Gardening:How to prevent those pesky spring weeds in your lawn (or not) What is Nostoc commune, also known as star jelly? Nostoc commune, also referred to as star jelly, witch's butter and mare's eggs, is a species of cyanobacterium that grows in countries all over the world.
—Victoria Moorwood, The Enquirer, 12 Apr. 2023
Molecular geneticist Susan Golden of the University of California, San Diego, has helped to decode the molecular machinery regulating time in the cyanobacterium Synechococcus elongatus, and coauthored a description of the clock in the Annual Review of Genetics.
—Adam Mann, Discover Magazine, 25 Mar. 2020
Nostoc azollae, a cyanobacterium species that lives inside Azolla leaves, captures nitrogen from the air and converts it into a form that the ferns — and rice plants — can use.
—Erika K Carlson, Discover Magazine, 2 July 2018
Evidence hinted that the Azolla fern and its cyanobacterium partner might share a long evolutionary past together.
—Erika K Carlson, Discover Magazine, 2 July 2018
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Quanta Magazine, 28 Oct. 2024
In 2024, his lab reported a nitrogen-providing cyanobacterium that had become an organelle within an algal cell.
—Quanta Magazine, 17 July 2024
The algae engulfed a cyanobacterium gives it a bit of a plant superpower.
—Laura Baisas, Popular Science, 18 Apr. 2024
Nostoc commune, also referred to as star jelly, witch's butter and mare's eggs, is a species of cyanobacterium that grows in countries all over the world.
—Victoria Moorwood, USA TODAY, 15 Apr. 2023
Here's what to know Gardening:How to prevent those pesky spring weeds in your lawn (or not) What is Nostoc commune, also known as star jelly? Nostoc commune, also referred to as star jelly, witch's butter and mare's eggs, is a species of cyanobacterium that grows in countries all over the world.
—Victoria Moorwood, The Enquirer, 12 Apr. 2023
Molecular geneticist Susan Golden of the University of California, San Diego, has helped to decode the molecular machinery regulating time in the cyanobacterium Synechococcus elongatus, and coauthored a description of the clock in the Annual Review of Genetics.
—Adam Mann, Discover Magazine, 25 Mar. 2020
Nostoc azollae, a cyanobacterium species that lives inside Azolla leaves, captures nitrogen from the air and converts it into a form that the ferns — and rice plants — can use.
—Erika K Carlson, Discover Magazine, 2 July 2018
Evidence hinted that the Azolla fern and its cyanobacterium partner might share a long evolutionary past together.
—Erika K Carlson, Discover Magazine, 2 July 2018
Cite this Entry
“Cyanobacterium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cyanobacterium. Accessed 12 Jul. 2025.
Copy CitationKids Definition
cyanobacterium
noun
cy·a·no·bac·te·ri·um
ˌsī-ə-nō-bak-ˈtir-ē-əm
sī-ˌan-ō-
Medical Definition
cyanobacterium
noun
cy·a·no·bac·te·ri·um
-bak-ˈtir-ē-əm
plural cyanobacteria
-ē-ə
: 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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