Effects of two cyanotoxins, microcystin-LR and cylindrospermopsin, on euglena gracilis

Abstract

Freshwater eutrophisation causes blooms of cyanobacteria, including species that produce toxins harmful to animals. We present here a study of the effects of two hepatotoxins: microcystin-LR (heptapeptide) and cylindrospermopsin (alkaloid), on Euglena, a photosynthetic protist. Microcystin-LR (0.01-10 εg ml-1) and cylindrospermopsin (0.13-12.5 εg ml -1) showed no toxic effect on growth but significantly increased cell productivity. O2 consumption was significantly stimulated half an hour after the toxin was added for microcystin and 48 h after for cylindrospermopsin for all the concentrations tested. In addition, a drastic inhibition of greening and photosynthesis as well as an 80% increase of reduced glutathione were observed at the high concentrations of cylindrosper-mopsin. Two-dimensional electrophoresis after 35S amino acid labeling showed that with cylindrospermopsin a 23-kda protein was induced in the first 2 h, whereas a 29-kda protein was overexpressed with microcystin and cylindrospermopsin. © 2005 Springer-Verlag Berlin Heidelberg.