(bacteria and informally called “blue-green algae”)
Blue-green algae make up the division Cyanophyta in the kingdom Eubacteria. Cynanbacteria differ from other types of bacteria in that they have chlorophyll a, which other photosynthetic bacteria don’t have. They are prokaryotic (no membrane-bound organelles), they have only a haploid life cycle (while all algae life cycles have an alteration of generation), they reproduce through fission, they don’t have cellulose in their cell walls, their DNA is not associated with histone proteins in their chromosomes (unlike algae and other plants) (Clark, 1998).
Cyanobacteria gets its common name from the blue-green pigment, phycocyanin, which along with chlorophyll a gives cyanobacteria a blue-green appearance. Phycocyanin is a protein that functions as the photosynthetic pigment in photosystem II, whereas in plants chlorophyll b is the pigment in photosystem II (Clark, 1998).
Cyanobacteria have a wide variety of habitats that range from frozen lakes, to acidic bogs, to deserts and volcanoes. They are most commonly found in alkaline aquatic environments (but also in aquatic environments ranging in salinity and acidity), they can also be found in soil, on rocks, and even in the atmosphere (Bold, 1985).