Bifunctional Effect of Fusarium stercicola F8 Strain on Microcystis aeruginosa Cyanobacterium

A new strain of fungus Fusarium sp. F8 was isolated from the waters of the Gulf of Finland during the period of active cyanobacteria vegetation. The fungal strain F8 was identified by morphological and cultural characteristics and by phylogenetic analysis based on the nucleotide sequences of two DNA loci (ITS and tef) as F. stercicola. Strain F. stercicola F8 exhibited high (97%) algicidal activity against cyanobacteria Microcystis aeruginosa. The indirect mechanism of the algicidal action of strain Fusarium stercicola F8 by releasing exometabolites into the medium was shown. The filtrate of the fungal culture liquid was not toxic to the Daphnia magna and Paramecium caudatum. The property of strain F8 to degrade highly toxic microcystin-LR (MC–LR) was revealed. A decrease in the MC–LR content in the culture medium of the isolated strain Fusarium stercicola F8 was found from 0.5 µg/ml to 0.28 µg/ml in 72 hours. The revealed dual action mechanism of the F. stercicola F8 strain on Microcystis aeruginosa is of interest for further research in order to develop biotechnologies for controlling the mass development of toxigenic cyanobacteria in water bodies.