Blue-Green Algae Characteristics

Blue-green Algae (Cyanobacteria)

• Algae are not a related group; they are assigned to different kingdoms based on lack of nuclei (prokaryotic).
• Blue-green algae are in the kingdom Monera.
• They're similar to bacteria.
• They lack membrane-bound organelles like nuclei, mitochondria, Golgi bodies, and plastids.
• Cell walls are composed of layers of mucoprotein and polysaccharides (including lipopolysaccharides).
• Cellulose, commonly found in plant cells, is absent.
• Pigments include chlorophyll a, carotenoids, phycocyanin (blue), and phycoerythrin (red).
• Organisms are not always blue-green. They can be various colors.
• Morphology varies from unicellular to filamentous, often with mucilaginous sheaths.
• They have akinetes and trichomes (characteristic of filamentous forms).
• Reproduction is primarily asexual (binary fission, multiple fission; producing endospores and hormogonia).
• Sexual reproduction is lacking.
• Trichodesmium erythraeum, a reddish blue-green alga, imparts a red color to water (e.g., the Red Sea).
• Chlorophyll a is responsible for photosynthesis, producing glycogen (similar to animal livers).
• The cell's colored portion is around the periphery, and the central part contains the chromatin.
• Vacuoles are absent in healthy young cells; some species produce endospores.
• They can thrive in diverse environments (snow, ice, hot springs, desert soils).
• They are often found in nodules of Cycads in the same way that nitrogen-fixing bacteria are found in legumes.
• They are a source of food for some fish (sometimes making the fish poisonous).
• Found in amoebas, diatoms, and other algal cells (and in the hollow leaves of Azolla), or shells of turtles/snails and hair follicles of sloths.

Nostoc

• A genus of blue-green algae/cyanobacteria.
• Found in freshwater as free-living colonies or attached to surfaces.
• Found on trees and in certain bryophytes.
• Can fix atmospheric nitrogen and perform photosynthesis.
• Forms colonies.
• Structure includes numerous filaments in a gelatinous mass resembling a colony the size of an egg.
• Filaments are made up of bead-like cells called trichomes that are oval, spherical, or cylindrical in shape.
• Some trichome cells are differentiated, called heterocysts, and involved in nitrogen fixation.
• Each filament is surrounded by a protective mucilaginous sheath which is made of polysaccharides and proteins.
• They resemble bacteria that live in bean plant root nodules.
• They can increase the fertility of rice paddies.

Oscillatoria

• A common blue-green alga growing in filaments.
• Found in lakes, ponds, moist soil.
• Filaments can appear as singly, or in mats.
• Thirty species exist in North America.
• Cells in filaments divide transversely, and each cell is an individual
• Filaments can show undulating movement (oscillatory movement).
• Reproduction through fragmentation (hormogonia formation).

General Characteristics

• Colonies are diverse in shape, size, and color (mostly bluish-green, but can be different).
• Extracellular pigments (nostochine, scytonemin) protect cells from UV radiation.
• Each cell has thick cell walls made of peptidoglycan.
• Cytoplasm has a differentiated structure (outer colored chromoplasts, inner clear cytoplasm).
• Cells contain various pigments, including chlorophyll, phycocyanin (blue), phycoerythrin (red).
• DNA is in the inner cytoplasm without histones.
• Reproduction involves asexual reproduction (spore formation, fragmentation forming colonies, hormogonia)
• They're ecologically important for nitrogen fixation, soil improvement, and use as a food source (e.g., in Asian countries as N. flagelliforme or N. commune).
• Some species produce polyhydroxybutyrate.
• Some can produce hydrogen
• Some can be used for environmental remediation/wastewater bioremediation.
• Some species show anti-bacterial or anti-viral properties

Explore the fascinating world of blue-green algae, known scientifically as cyanobacteria. This quiz covers their classification, structure, reproduction, and pigments, highlighting their unique characteristics and ecological importance. Test your knowledge on this diverse group of organisms that play a crucial role in aquatic ecosystems.