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Nostoc AZOLLAE.jpg
Photo of N. azollae
Scientific classification
Kingdom: Bacteria
Phylum: Cyanobacteria
Class: see taxonomic note
Order: Nostocales
Family: Nostocaceae
Genus: Nostoc

N. azollae
N. caeruleum
N. carneum
N. comminutum
N. commune
N. ellipsosporum
N. flagelliforme
N. linckia
N. longstaffi
N. microscopicum
N. muscorum
N. paludosum
N. pruniforme
N. punctiforme
N. sphaericum
N. sphaeroides
N. spongiaeforme
N. verrucosum

Nostoc is a genus of cyanobacteria found in a variety of environmental niches that forms colonies composed of filaments of moniliform cells in a gelatinous sheath.

The name Nostoc was coined by Paracelsus.[1]

Nostoc can be found in soil, on moist rocks, at the bottom of lakes and springs (both fresh- and saltwater), and rarely in marine habitats. It may also grow symbiotically within the tissues of plants, such as the evolutionarily ancient angiosperm Gunnera and the hornworts (a group of bryophytes), providing nitrogen to its host through the action of terminally differentiated cells known as heterocysts. These bacteria contain photosynthetic pigments in their cytoplasm to perform photosynthesis.


Nostoc is a member of the family Nostocaceae of the order Hormogonales. Species include:

Non-scientific nomenclature[edit]

When it is on the ground, a nostoc colony is ordinarily not seen; but after a rain it swells up into a conspicuous jellylike mass, which was once thought to have fallen from the sky; hence the popular names, star jelly, troll’s butter, witch's butter (not to be confused with the fungus Tremella mesenterica), and witch’s jelly.

Michael Quinion of the "World Wide Words" newsletter says that it is known in Welsh as pwdre sêr (rot of the stars).[3] It is also known as pydredd sêr (star-slime).[4]

Culinary use[edit]

Containing protein and vitamin C,[citation needed] Nostoc species are cultivated and consumed as a foodstuff, primarily in Asia. The species N. flagelliforme and N. commune are consumed in China, Japan and Java, N. commune is also consumed in the Andes. The preferred variety in Central Asia is N. ellipsosporum.

A research team from the biochemistry department of the Chinese University of Hong Kong said that international research has shown that fat choy (Nostoc flagelliforme), besides having no nutritional value, has also been found to contain Beta-methylamino L-alanine (BMAA), a toxic amino acid that could affect the normal functions of nerve cells. Professor Chan King-ming of the team told the media that eating fat choy could lead to degenerative diseases such as Alzheimer's, Parkinson's, and dementia.[5][citation needed] While all cyanobacteria produce BMAA, the beneficial compounds may override any toxic effects.[6]


  1. ^ Potts, M. (1997). "Etymology of the Genus Name Nostoc (Cyanobacteria)" (pdf). International Journal of Systematic Bacteriology 47 (2): 584. doi:10.1099/00207713-47-2-584. 
  2. ^ Abbott, I. A. (1989). "Food and food products from seaweeds". In Lembi, C. A.; Waaland, J. R. Algae and human affairs. Cambridge University Press, Phycological Society of America. p. 141. ISBN 978-0-521-32115-0. 
  3. ^ Weird Words: Nostoc on World Wide Words
  4. ^ Thomas, R. J.; Bevan, G. A.; Donovan, P. J. (2003). Geiriadur Prifysgol Cymru. Caerdydd (Cardiff): Gwasg Prifysgol Cymru. ISBN 978-0-7083-1806-5. 
  5. ^ The Archived November 22, 2007 at the Wayback Machine
  6. ^ Ku, Lee (2013). "Edible blue-green algae reduce the production of pro-inflammatory cytokines by inhibiting NF-κB pathway in macrophages and splenocytes". Biochimica et Biophysica Acta – General Subjects 1830 (4): 2981–2988. doi:10.1016/j.bbagen.2013.01.018. PMID 23357040. 

External links[edit]

Guiry, M.D.; Guiry, G.M. (2008). "Nostoc". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.