Cyanobacteria
From Halbeeg, the open encyclopedia · Af-Soomaali
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Cyanobacteria are a group of bacteria capable of photosynthesis, a process that uses sunlight to produce food from carbon dioxide and water. They differ from other bacteria in that they release oxygen when performing this process. Because of their blue-green color, they were formerly called "blue-green algae," although they are prokaryotic organisms lacking a nucleus.
They inhabit oceans, rivers, lakes, soil, and harsh environments such as hot springs and deserts. Some are single cells, while others form filaments or colonies of connected cells. They play a major role in global carbon and nitrogen cycles.
Structure and function
Cyanobacteria possess a pigment called chlorophyll a, which absorbs red light, and other pigments such as phycobilins that give them their blue-green color. Photosynthesis is carried out in structures within the cell called thylakoids. Many species can also convert atmospheric nitrogen into a form that organisms can use; some perform this process in specialized cells called heterocysts.
Role in Earth's history
Cyanobacteria are believed to have increased oxygen in Earth's atmosphere in early times, a change known as the Great Oxidation Event. The existence of much complex life that depends on oxygen therefore relies on their ancient activity. The endosymbiotic theory also proposes that the photosynthetic organelle (chloroplast) in plants originated from cyanobacteria that entered another cell.
Environmental and health impacts
When nutrients such as phosphorus and nitrogen accumulate in stagnant water—typically in reservoirs or wastewater—cyanobacteria can multiply rapidly, producing what is known as a bloom. Some species produce toxins that can harm animals and people using the water. Additionally, large blooms deplete oxygen in the water, killing fish.
Human uses
Certain species, such as Spirulina (Arthrospira), are cultivated for food and nutritional supplements. Research is also directed toward their use in biofuel production and water treatment. Others are used in genetic research because of their simple structure and rapid growth.