Generic name: MICROCYSTIS Kützing 1833 ex Lemmermann Cryptogamenfl. Mark Brandenb. 3/1: 45, 1907
Nomina rejicienda:
Microcystis Kutz. Linnaea 8:372, 1833
Microcystis Menegh. Cennisula org. fisiol. Alg., 25, 1838
Diplocystis Trevis Sagg. Monogr. Alg. Coccot. 40, 1848
Cagniardia  Trevis Sagg. Monogr. Alg. Coccot. 47, 1848
Anacystis Menegh. sensu Kutz. Spec. Alg. 209, 1849
Clathrocystis Henfr. Trans. microsc. Soc. London ser. 2. 4: 53 1856
Nomina excludenda:
Micraloa Bias. Di Alc. Alghe Microsc., p. 44. et 46., 1832
Sphaerothrombium Kutz. Linnaea 8: 370, 1833
Anacystis Menegh. Consp. Algol. Eugan. 324., 1837
Microhaloa Kutz. Phyc. gener. 169., 1843
Microcystis Kutz. em. Kutz. Tab. Phycol. 1:6-7.,1846
Trichocystis Kutz. Tab. Phycol. 1: 20.,  1846
Polycystis Kutz. Spec. Alg. 210., 1849
Type species: Microcystis aeruginosa(Kützing) Kützing 1846. - About 50 described species, but the inner taxonomy of that genus needs revision.
Komárek & Anagnostidis (1998): Colonies micro- or macroscopic, free floating, spherical, oval, lobate to irregular, or elongate, in several species irregularly clathrate, sometimes composed of subcolonies or clustered together, with irregularly, sparsely or (usually) densely arranged cells in common
mucilage. Mucilage fine, colourless, usually homogeneous or only indistinctly lamellate, diffluent or distinct and delimited, in several species with refractive outline (surface); around individual cells gelatinous envelopes never present. Cells spherical or hemispherical after division, with gas vesicles (joined into distinct aerotopes). Hexagonal substructure (p6) of S-layers was found in cell walls of several Microcystis strains.
Komárek (1992): Unicellular - colonial; colonies gelatinous, free floating or attached to the substrate, microscopic, spherical, discoid or irregular, later usually macroscopic, amorph, irregular, sometimes net-like, with numerous cells without own mucilaginous envelopes, irregularly distributed within the common slime, sometimes densely agglomerated; colonial mucilage colourless, usually homogeneous, fine, diffluent (staining !), rarely with the limited, sometimes refractive margin. Cells spherical or (after division) hemispherical, with homogeneous, blue-green, greyish or yellowish content, in several planktic species with several up to numerous aerotopes; sometimes with visible chromatoplasma. Several strains are toxic, and producing b-cyclocitral.
Geitler (1932): Zellen kugelig oder länglich, zu vielen in kugeligen, ellipsoidischen, unregelmäßigen oder netzförmig durchbrochenen Kolonien, welche manchmal aus Teilkolonien zusammengesetzt sind, vereinigt. Die Zellen liegen in einer gemeinsamen, homogenen, weichen, typischerweise ungefärbten Gallerthülle, welche manchmal zerfließt; Spezialhüllen zerfließend. Zellen meist sehr dicht gelagert, durch gegenseitige
Abplattung oft eckig. Zellteilungen nach allen Raumrichtungen. Teilung bei länglichen Zellen quer zur Längsachse. Nannocyten bisher nur bei Microcystis flos-aquae bekannt. Kolonien meist freischwimmend; Zellen bei vielen Arten mit Gasvakuolen.
Genotype differences, molecular data:
Reproduction strategies, life cycles, cell division:
Komárek & Anagnostidis (1998): Cell division by binary fission in three perpendicular planes in regular «cubic» arrangement; cells grow into the original size and shape before next division. Reproduction by disintegration of colonies into small clusters of cells or even into  solitary cells.
Komárek (1992): Cell division in three planes in successive generations, perpendicular one to another; daughter cells soon separate one from another, and grow into the original size and shape before the next division. Reproduction by the disintegration of colonies.
Taxonomic position, higher hierarchy: Oscillatoriophycideae, Chroococcales, Microcystaceae
Notes to taxonomy, misinterpretations:
Ecology, ecophysiology, ecological

Komárek (1992): Free floating in plankton of freshwater, more or less eutrophic water reservoirs (sometimes forming heavy water blooms). Several species live benthic in moors, epiphytic or epilithic in different types of stagnant and running waters and on wet rocks. Many species have world wide distribution (with exception of subpolar regions), but several taxa are ecologically and therefore also fytogeographically limited. The majority of not-planktic species without ability to form gas vesicles belongs probably to the genus Aphanocapsa.
Physiology and biochemistry:
Distribution, endemism, problematic citations:
Reference strain:
Infrageneric scheme, species concept:
List of species:
Microcystis aeruginosa
 (Kützing) Kützing 1846
Microcystis bengalensis Banerji 1936
Microcystis botrys Teiling 1942
Microcystis comperei Komárek 1984
Microcystis densa G.S. West 1909
Microcystis firma
(Kützing) Schmidle 1902
Microcystis flos-aquae (Wittrock) Kirchner 1898
Microcystis ichthyoblabe Kützing 1843
Microcystis lamelliformis Holsinger 1954
Microcystis natans
Lemmermann ex Skuja 1934
Microcystis novacekii (Komárek) Compere ex Komárek 1974
Microcystis panniformis Komárek et al. 2002
Microcystis protocystis Crow 1923
Microcystis pseudofilamentosa Crow 1923
Microcystis smithii Komárek et Anagnostidis 1995
Microcystis viridis (A. Braun in Rabenhorst) Lemmermann 1903
Microcystis wesenbergii (Komárek) Komárek in Kondrateva 1968

Unclar taxa:
Microcystis argentea
Schiller 1954
Microcystis elongata Desicachary 1959
Microcystis maxima Bernard 1908
Microcystlis pallida (Farlow) Lemmermann 1940
Microcystis prasina (Wittrock) Lemmermann in Frémy 1930
Microcystis punctata Schiller 1954
Microcystis ramosa Bharadwaja 1935
Microcystis robusta (Clark) Nygaard 1925
Microcystis rosea Kufferath 1942
Microcystis scripta (Richer) Geitler 1925
Microcystis supersalsa Schiller 1956
Microcystis toxica Stephes 1949

List of stains:
Komárek 1992
Application technology:
  2.1 taxonomy: Lemmermann 1907, Crow 1923, Geitler 1932, Elenkin 1933, Huber-Pestalozzi 1938, Teiling 1941, Teiling 1942, Komárek 1957, Komárek 1958, Desikachary 1959, Almestrand 1961, Starmach 1966, Kondrateva 1968, Reynolds et al. 1981, Parker 1982, Kondrateva et al. 1984, Komárek & Anagnostidis 1986, Watanabe et al. 1986, Doers & Parker 1988, Hofbauer & Jüttner 1988, Grilli Caiola & al. 1991, Kato 1991, Kato et al. 1991, Komárek 1991, Komárek 1992, Komárek & Anagnostidis 1998
  2.2 cytomorphology:
  2.3 16S rRNA sequencing:
  2.4 biology and life cycles:
  2.5 ecology: