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Microbiology => Bacteria => Cyanobacteria or Blue-Green Algae
Cyanobacteria or Blue-Green Algae
Cyanobacteria or Blue-Green Algae, members of a group of photosynthetic prokaryotes single-celled organisms that lack an enclosed nucleus and other specialized cell structures. Like green plants, cyanobacteria contain chlorophyll but the chlorophyll is not located in chloroplasts; rather it is found in chromatophores, infoldings of the plasma membrane where photosynthesis is carried out. In many species, other pigments mask the chlorophyll and impart a bluish or sometimes reddish color. Some species are free-living, but most aggregate in colonies or form filaments. Reproduction is by simple cell division or by fragmentation of the filaments.
Cyanobacteria are found throughout the world in diverse habitats. They are abundant on tree bark and rocks and in moist soil, where they carry on nitrogen fixation. Some symbiotically coexist with fungi to form a lichen. In hot weather some species form large and occasionally toxic blooms on the surfaces of ponds and coastal waters. In shallow tropical waters, mats of the cyanobacteria grow into humps called stromatolites. Fossil stromatolites are found in rocks formed more than 3 billion years ago, during Precambrian time. They suggest that cyanobacteria played a role in changing the ancient carbon dioxide-rich atmosphere into the oxygenated mixture that exists today.
Scientific classification: Cyanobacteria make up the phylum Cyanophyta, in the kingdom Prokaryotae.
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