The cyanobacteria are unicellular beings with prokaryotic organization. They belong, therefore, to the kingdom Monera . They are micro-organisms, that is, they can only be seen with a microscope.
Many of its representatives are disease-causing; others are of great ecological importance and some are prominent in the food industry and the pharmaceutical industry.
A bacterial cell has very simple organization: cell wall, plasma membrane, cytoplasm, hyaloplasm, ribosomes, genetic material and sometimes plasmids.
Cyanobacteria are very ancient organisms that have appeared on Earth for 3.5 billion years. They were probably the first photosynthetic organisms, responsible for the accumulation of oxygen (O2) in the primitive atmosphere and the appearance of ozone (O3), which retains part of the ultraviolet radiation.
Besides being important for the production of oxygen , some of them, such as those of the genera Nostoc and Anabaena , have the capacity to absorb and fix the nitrogen of the atmospheric air. .
We can call them pioneers , since they are the first living beings to colonize an ecosystem still in formation.
They are able to develop in bare rocks, soils, water, as they produce the organic matter they need ( autotrophs ), enabling later installation of other living beings.
They are found in the most varied environments: in the oceans, in fresh water, in moist soils, in tree trunks, on rocks, associated with fungi, forming lichens, and even in hot springs of high temperatures. They may present as single isolated cells or grouped into colonies, and some have cells lined with a transparent gelatin layer.
The cyanobacteria do not have chloroplasts, but they have, besides chlorophyll (green pigment), other pigments, such as blue, orange, brown, red, etc. In the Red Sea, some reddish cyanobacteria appear in such a quantity that they confer this color to the water.