cyanobacteria

cyanobacteria /sī′ənōbaktir′ē·ə/ [Gk, kyanos, blue + bacterion, small staff] , blue-green bacteria, unicellular or filamentous organisms that fix both carbon dioxide (in the presence of light) and nitrogen. Several species are common causes of water pollution and cause cyanobacteria poisoning. Formerly called blue-green algae.