Microcystis aeruginosa

Microcystis aeruginosa
Scientific classification
Kingdom:	Bacteria
Subkingdom:	Eubacteria
Phylum:	Cyanobacteria
Class:	Cyanophyceae
Order:	Chroococcales
Family:	Microcystaceae
Genus:	Microcystis
Species:	M. aeruginosa
Binomial name
Microcystis aeruginosa Kützing, 1846

Microcystis aeruginosa is a species of freshwater cyanobacteria which can form harmful algal blooms of economic and ecological importance. They are the most common toxic cyanobacterial bloom in eutrophic fresh water. Cyanobacteria produce neurotoxins and peptide hepatotoxins, such as microcystin and cyanopeptolin.

As the etymological derivation implies, Microcystis is characterized by small cells (of only a few micrometers diameter), which lack individual sheaths.

Cells usually are organized into colonies (large colonies of which may be viewed with the naked eye) that begin in a spherical shape, but lose their coherence to become perforated or irregularly shaped over time.

The protoplast is a light blue-green color, appearing dark or brown due to optical effects of gas-filled vesicles; this can be useful as a distinguishing characteristic when using light microscopy. These vesicles provide the buoyancy necessary for M. aeruginosa to stay at a level within the water column at which they can obtain optimum light and carbon dioxide levels for rapid growth.

M. aeruginosa is favored by warm temperatures, but toxicity and maximal growth rates are not totally coupled, as the cyanobacterium has highest laboratory growth rates at 32 °C, while toxicity is highest at 20 °C, lowering in toxicity as a function of increasing temperatures in excess of 28 °C. Growth has been found to be limited below 15 °C.

The aquatic plant Myriophyllum spicatum produces ellagic, gallic, and pyrogallic acids and (+)-catechin, allelopathic polyphenols inhibiting the growth of M. aeruginosa.

M. aeruginosa can produce both neurotoxins (lipopolysaccharides-LPSs) and hepatotoxins (microcystins).

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