Cyanobacteria as producers of saxitoxin and its derivatives in Lake Baikal and the water bodies of the Baikal region
O. I. BELYKH1, G. A. FEDOROVA1, I. V. TIKHONOVA1, A. S. GLADKIKH2, S. A. POTAPOV1, YA. A. NAIDANOVA1, A. V. KUZMIN1, E. G. SOROKOVIKOVA1
1Limnological Institute, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
2Saint-Petersburg Pasteur Institute, St. Petersburg, Russia
Keywords: Baikal, cyanobacteria, cyanotoxins, saxitoxin, phylogeny, enzyme-linked immunoassay
Abstract
Paralytic neurotoxins (saxitoxins) produced by cyanobacteria have been found in Lake Baikal and the reservoirs of the Angara cascade of hydropower plants. These neurotoxins are dangerous for humans and animals. The concentration of paralytic toxins was determined to be 0.2-182.6 μg/L, exceeding the limits recommended by the World Health Organisation. Cyanobacterium Dolichospermum lemmermannii was highly abundant in Lake Baikal and reservoirs of the region, its mass development causing localised surface blooms. Cyanobacterial cultures isolated from Lake Baikal were identified as D. lemmermannii. Saxitoxin biosynthesis gene sequences were detected in samples from the studied water bodies and in cultured strains; they had high similarity to each other and belonged to the single species - D. lemmermannii. This is the first report of the ability of D. lemmermannii to synthesise paralytic shellfish toxins. Four toxin variants were identified in the plankton of Lake Baikal and reservoirs: saxitoxin and neosaxitoxin containing carbamoyl groups, as well as decarbamoyl derivatives of goniatoxins. It is shown that in the ancient oligotrophic Lake Baikal and the Angara River reservoirs, there is a source of occurrence and spread of harmful algal blooms due to the presence of toxin-producing cyanobacteria. Under favourable hydrophysical and hydrochemical conditions, and influenced by climatic and anthropogenic factors, the frequency and prevalence of toxic cyanobacterial blooms in the aquatic ecosystems of the Baikal region, as globally, exhibit an increasing trend. This underscores the need for further research and implementation of significant efforts aimed at monitoring cyanotoxins and toxic bacterial species, as well as at understanding the mechanisms underlying the initiation and proliferation of cyanobacterial blooms.
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