Cyanobacteria, also called blue algae or cyanophyceous algae, are prokaryotic microorganisms capable of carrying out photosynthesis, but do not have photosystems organized in chloroplasts. For this reason, they are often compared with bacteria and seaweed.
Cyanobacteria appeared approximately three billion years ago on Earth. This dating is confirmed from fossils known as stromatolites, which were formed by these microorganisms. Because they have existed for so long, it is believed that cyanobacteria were responsible for producing the oxygen that accumulated in the primitive atmosphere.
→ Main characteristics of cyanobacteria
Cyanobacteria are photosynthetic organisms (autotrophic) which are very similar to unicellular algae, however, as they do not have a membrane-delimited nucleus (prokaryote), are also very similar to bacteria. They are unicellular, but can be found forming colonies or filaments. These organisms, in the aquatic ecosystem, form the call phytoplankton and constitute the basis of the food chain of these ecosystems.
Cyanobacteria staining is achieved by presence of different pigments, such as chlorophyll, phycocyanins and phycoerythrins. In addition to promoting the color of these organisms, pigments are related to the process of photosynthesis.
Cyanobacteria are found in several habitats, being most, however, are freshwater. The great success of cyanobacteria is related to factors such as surviving in environments with different types of luminosity, being able to store nutrients and being able to capture nitrogen atmospheric.
→ Cyanobacterial blooms
Under ideal conditions (increased concentrations of Nitrogen and Phosphorus, elevated temperatures and availability of light), cyanobacteria reproduce in an exaggerated way, causing the famous blooms. These blooms are closely related to the process of eutrophication, mainly caused by man, who releases a large amount of sewage into the water. It is worth noting that blooms trigger changes in the color and taste of the water.
→ Cyanobacteria and their toxins
There are several species of cyanobacteria capable of producing toxins, also called cyanotoxins. Cyanotoxins act as a protection against predation and can cause serious harm if ingested by humans.
Cyanotoxins can be classified according to their action in neurotoxins, hepatotoxins and dermotoxins. Neurotoxins can cause skin tremors, wheezing, imbalance and convulsions when ingested. Hepatotoxins, on the other hand, affect the liver and can cause enlargement of that organ and hemorrhages that can lead to death. Vomiting and diarrhea can be signs of ingesting this type of toxin. Finally, we have dermotoxins, which cause irritation in contact with the skin.
In places where water is used for supply, there must be constant analysis to prevent cyanobacteria from reproducing in an accentuated way. A large amount of cyanobacteria can cause an increase in toxins in the water, causing health risks for those who consume it.
By Ma. Vanessa dos Santos
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-cianobacteria.htm