Author/Editor		Sedmak, Bojan; Eleršek, Tina
Title		Microcystins induce morphological and physiological changes in selected representative phytoplanktons
Type		članek
Source		Microbial Ecol
Vol. and No.		Letnik 50
Publication year		2005
Volume		str. 298-305
Language		eng
Abstract		Dissolved microcysiins (MC) are regularly present in water dominated by microcystin-producing, bloomforming cyanobacteria. In vitro experiments with environmentally feasible concentrations (5 x 10-7 M) of the three most common microcystins, MC-LR, -RR, and -YR, revealed that they influence the metabolism of different representative phytoplanktons. At light intensities close to the cyanobacterial bloom environment (50 micromol m-2 s-1), they produce morphological and physiological changes in both microcystin-producing and nonproducing Microcystis aeruginosa strains, and also have similar effects on the green alga Scenedesmus quadricauda that is frequently present in cyanobacterial blooms. All three microcystin variants tested induce cell aggregation, increase in cell volume, and overproduction of photosynthetic pigments. All three effects appear to be related to each other, but are not necessarily caused by the same mechanism. The biological activity of microcystins toward the light-harvesting complex of photobionts can be interpreted as a signal announcing the worsening of light conditions due to the massive proliferation of cyanobacteria. Although the function of microcystins is still unknown, it is evident that they have numerous effects on phytoplankton organisms in nature. These effects depend on the individual organism as well as on the various intracellular and extracellular signaling pathways. The fact that dissolved microcystins also influence the physiology of microcystin-producing cyanobacteria leads us to the conclusion that the role of microcystins in the producing cells differs from their role in the water environment.
Descriptors		PHYTOPLANKTON CYANOBACTERIA BACTERIAL TOXINS EUTROPHICATION CHLOROPHYLL PHYCOCYANIN CELL SIZE