Anabaena flos-aquae: A species in the genus ANABAENA containing gas vacuoles that gives buoyancy to the organism. It can form extensive blooms in FRESH WATER and is responsible for acute poisonings of various animals.Anabaena cylindrica: A species in the genus ANABAENA whose trichomes are composed of cylindrical cells.Oscillatoria: A genus of filamentous CYANOBACTERIA in the order Oscillatoriales. It is commonly found in freshwater environments, especially hot springs.Anabaena: A genus of CYANOBACTERIA consisting of trichomes that are untapered with conspicuous constrictions at cross-walls. A firm individual sheath is absent, but a soft covering is often present. Many species are known worldwide as major components of freshwater PLANKTON and also of many saline lakes. The species ANABAENA FLOS-AQUAE is responsible for acute poisonings of various animals.Cyanobacteria: A phylum of oxygenic photosynthetic bacteria comprised of unicellular to multicellular bacteria possessing CHLOROPHYLL a and carrying out oxygenic PHOTOSYNTHESIS. Cyanobacteria are the only known organisms capable of fixing both CARBON DIOXIDE (in the presence of light) and NITROGEN. Cell morphology can include nitrogen-fixing heterocysts and/or resting cells called akinetes. Formerly called blue-green algae, cyanobacteria were traditionally treated as ALGAE.Aphanizomenon: A form-genus of planktonic CYANOBACTERIA in the order Nostocales.Microcystis: A form-genus of CYANOBACTERIA in the order Chroococcales. Many species are planktonic and possess gas vacuoles.Anabaena variabilis: A species of ANABAENA that can form SPORES called akinetes.