Toxic potential of microcystin-containing cyanobacterial extracts from three Romanian freshwaters

The aim of this study was to characterise for the first time the toxin profile and in vivo/in vitro toxicological effects of cyanobacteria obtained from three Romanian freshwater blooms. Two strains of Microcystis aeruginosa were isolated from blooms occurring in different fish ponds. As well, a complex bloom sample obtained from a recreational lake area and dominated by Microcystis aeruginosa and Microcystis viridis was explored. The morphological identity of the cyanobacterial species could be confirmed by sequence analysis of the intergenic spacer region of the phycocyanin operon, PC-IGS. As well, both the strains and the field sample were confirmed to possess mcyA and mcyB genes, which correlated with the formation of several microcystins (MCYSTs). A number of cyanopeptolins and a new aeruginosin were also found. Despite these mixtures of compounds, in vivo as well as in vitro toxicological responses resembled those previously found for MCYST-LR. These include strong hepatotoxicity in mice with parenchymal disintegration and the emergence of haemorrhagic centres, a lack of responsiveness of human and fish cell lines most likely due to a lack of active transport systems, and a significant subcellular damage most prominent on the level of the lysosomes in primary hepatocytes of mice and rainbow trout. We thus conclude that the formation of blooms in the Romanian fish ponds and the recreational area may impact on animal and human health. A broader survey of cyanotoxin occurrence and related toxicity is necessary in Romania in order to assess the extent of this animal and human health hazard.