Cyanobacteria //, also known as Cyanophyta, is a phylum of bacteria that obtain their energy throughphotosynthesis. The name "cyanobacteria" comes from the color of the bacteria (Greek: κυανός (kyanós) = blue). They are often called blue-green algae, but some consider that name a misnomer as cyanobacteria are prokaryotic and algaeshould be eukaryotic, although other definitions of algae encompass prokaryotic organisms.
By producing oxygen as a gas as a by-product of photosynthesis, cyanobacteria are thought to have converted the earlyreducing atmosphere into an oxidizing one, which dramatically changed the composition of life forms on Earth by stimulating biodiversity and leading to the near-extinction of oxygen-intolerant organisms. According to endosymbiotic theory, the chloroplasts found in plants and eukaryotic algae evolved from cyanobacterial ancestors via endosymbiosis.Read more: Cyanobacteria