(redirected from cyanophyte)
Also found in: Dictionary, Thesaurus, Medical, Wikipedia.


cyanobacteria (sīˌənōbăktĭrˈēə, sī-ănˌō–) or blue-green algae, photosynthetic bacteria that contain chlorophyll. For many years they were classified in the plant kingdom along with algae, but discoveries made possible by the electron microscope and new biochemical techniques have shown them to be prokaryotes more similar to bacteria than to plants, and they are now placed in the kingdom Monera. Cyanobacteria are familiar to many as a component of pond scum. Despite their name, different species can be red, brown, or yellow; blooms (dense masses on the surface of a body of water) of a red species are said to have given the Red Sea its name. Nitrogen-fixing cyanobacteria need only nitrogen and carbon dioxide to live. Although some species are notable for the toxins they produce, other species have been harvested for centuries by Mesoamericans and Africans for food.
The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.


A large and heterogeneous group of photosynthetic microorganisms, formerly referred to as blue-green algae. They had been classified with the algae because their mechanism of photosynthesis is similar to that of algal and plant chloroplasts; however, the cells are prokaryotic, whereas the cells of algae and plants are eukaryotic. The name cyanobacteria is now used to emphasize the similarity in cell structure to other prokaryotic organisms. See Algae, Cell plastids

All cyanobacteria can grow with light as an energy source through oxygen-evolving photosynthesis; carbon dioxide (CO2) is fixed into organic compounds via the Calvin cycle, the same mechanism used in green plants. Thus, all species will grow in the absence of organic nutrients. However, some species will assimilate organic compounds into cell material if light is available, and a few isolates are capable of growth in the dark by using organic compounds as carbon and energy sources. Some cyanobacteria can shift to a different mode of photosynthesis, in which hydrogen sulfide rather than water serves as the electron donor. Molecular oxygen is not evolved during this process, which is similar to that in purple and green photosynthetic sulfur bacteria. The photosynthetic pigments of cyanobacteria include chlorophyll a (also found in algae and plants) and phycobiliproteins. See Chlorophyll, Photosynthesis

Cyanobacteria are extremely diverse morphologically. Species may be unicellular or filamentous. Both types may aggregate to form macroscopically visible colonies. The cells range in size from those typical of bacteria (0.5–1 micrometer in diameter) to 60 μm.

When examined by electron microscopy, the cells of cyanobacteria appear similar to those of gram-negative bacteria. Many species produce extracellular mucilage or sheaths that promote the aggregation of cells or filaments into colonies.

The photosynthetic machinery is located on internal membrane foldings called thylakoids. Chlorophyll a and the electron transport proteins necessary for photosynthesis are located in these lipid membranes, whereas the water-soluble phycobiliprotein pigments are arranged in particles called phycobilisomes which are attached to the lipid membrane.

Several other types of intracellular structures are found in some cyanobacteria. Gas vesicles, which may confer buoyancy on the organisms, are often found in cyanobacteria that grow in the open waters of lakes. Polyhedral bodies, also known as carboxysomes, contain large amounts of ribulose bisphosphate carboxylase, the key enzyme of CO2 fixation via the Calvin cycle. Several types of storage granules may be found.

Cyanobacteria can be found in a wide variety of fresh-water, marine, and soil environments. They are more tolerant of environmental extremes than are eukaryotic algae. For example, they are the dominant oxygenic phototrophs in hot springs (at temperatures up to 72°C or 176°F) and in hypersaline habitats such as may occur in marine intertidal zones.

Cyanobacteria are often the dominant members of the phytoplankton in fresh-water lakes that have been enriched with inorganic nutrients such as phosphate. It is now known that high population densities of small, single-celled cyanobacteria occur in the oceans, and that these are responsible for 30–50% of the CO2 fixed into organic matter in these environments. About 8% of the lichens involve a cyanobacterium, which can provide both fixed nitrogen and fixed carbon to the fungal partner. See Lichens, Phytoplankton

Cyanobacteria are thought to be the first oxygen-evolving photosynthetic organisms to develop on the Earth, and hence responsible for the conversion of the Earth's atmosphere from anaerobic to aerobic about 2 billion years ago. This development permitted the evolution of aerobic bacteria, plants, and animals. See Bacteria, Prebiotic organic synthesis

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a term used primarily in the microbiological literature since the 1970’s to denote the cyanophates (blue-green algae). The basis for introducing the term was a number of similarities between the Cyanobacteria and other prokaryotes, namely, bacteria. Both groups have similarities in their genetic structure, ribosomal and photosynthetic apparatus, and cell wall, having common chemical components, such as murein in the cell wall and poly-β-hydroxybutyrate as a reserve, and similar genetic properties.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A group of one-celled to many-celled aquatic organisms. Also known as blue-green algae.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
(2006) reported that the toxicity of Microcystis aeruginosa incremented to 90% when the cyanophyte was stressed as the salinity increased.
Other workers have reported [[mu].sub.max] = 0.13 [d.sup.-1] during semicontinuous cultivation of the cyanophyte Cyanobium in BG-11 medium with the addition of 0.4 g [L.sup.-1] of NaHC[O.sub.3] [19].
The species recorded in Awba reservoir as that causing water bloom Microcystis aeruginosa is a gas-vacuolate, non-nitrogen-fixing cyanophyte. It can assimilate ammonia and this affords it a competitive advantage over other species under conditions of nitrogen limitation.
From Figure 8, the dominant cyanophytes genera were Spirulina, Rivularia, Oscillatoria, and Anabaena.
Cyanobacteria are present in considerable numbers just about everywhere, although in the sea significant visible blooms of filiform cyanophytes (Trichodesmium or Oscillatoria, Nodularia) are scarce, and they are often found precisely where combined nitrogen is not lacking, perhaps due to the previous activity of these cyanobacteria populations.
cyanophytes dominated the phytoplankton community upon phosphorus
Cyanobacteria (formerly cyanophytes, Cyanophy-caceae, or blue-green algae) occur almost everywhere, but they are especially abundant in extreme ecological conditions, such as those in estuaries, tropical lagoons, hypersaline areas, and sites rich in nutrients.
The pre-amendment concentrations of [N.sup.15] in harpacticoids and oligochaetes were the lowest of all observed fauna, while their [C.sup.13] content was among the highest, suggesting the dietary influence of benthic microalgae and possibly cyanophytes (Table 3, Fig.
The subtropical gyre is an oligotrophic region with very low chlorophyll-a (Chl-a) concentrations in which the phytoplankton community is dominated by species of picoplankton (e.g., prochlorophytes and cyanophytes) and nanoplankton (Ras et al., 2008).