Cyanobacteria are photoautotrophs resembling chloroplasts; they even have two Photosystems and chlorophyll a. They were once thought to be plants and are still sometimes referred to as “blue-green algae.” They are aquatic and use water as their source of electrons.
produce oxygen through the reaction:
CO2 + 2H2O --> (CH2O) + H2O + O2
They come in long strands; each cell on the left is one cyranobacterium.
"Many Proterozoic oil deposits are attributed to the activity of cyanobacteria. They are also important providers of nitrogen fertilizer in the cultivation of rice and beans. The cyanobacteria have also been tremendously important in shaping the course of evolution and ecological change throughout earth's history. The oxygen atmosphere that we depend on was generated by numerous cyanobacteria during the Archaean and Proterozoic Eras. Before that time, the atmosphere had a very different chemistry, unsuitable for life as we know it today." -UC Berkeley Museum of Paleontology.
Cyanobacteria are thought to have evolved into chloroplasts and are believed to have been the organisms who created our oxygen-based atmosphere (as mentioned above).
The red sea (usually not red) contains Cyanobacteria with the pigment phycoerythrin