Taxonomy
Microcystis aeruginosa colonies isolated in New Zealand. © Susie Wood
Cyanobacteria are gram-negative oxygen-producing photosynthetic bacteria.
They were initially described as algae in the 18th century and are also known as Cyanophyta or blue-green algae, because of their blue-green coloration.
The species belongs to the order Chroococcales that are single-celled cyanobacteria and can form colonies.
Cells are usually spherical, pale blue-green and average 4–6µm in diameter.
Their colonies are moist and sticky, free-floating and usually 600–900µm long.
The colonies can look net-like with holes and often contain subcolonies. They have irregular outlines with a large number of irregularly arranged cells.