First report of saxitoxins and anatoxin-a production by cyanobacteria from Lithuanian lakes

This study describes the first report on saxitoxins (STXs) and anatoxin-a (ANTX-a) production by cyanobacteria in Lithuanian lakes. Seasonal fluctuation patterns for neurotoxins were determined in samples collected from eutrophic lakes during July–September. Strains of <i>Aphanizomenon gracile, A. flos-aquae, Cuspidothrix issatschenkoi, Sphaerospermopsis aphanizomenoides</i> and <i>Anabaenopsis</i> cf. <i>elenkinii</i> were also isolated from the lakes and screened for the occurrence of neurotoxic STXs, ANTX-a and for the cytotoxin cylindrospermopsin (CYN). The highest concentration of STX (up to 1.06 µg l^–1 in Lake Jieznas) was detected during July‒August and coincided with a predominance of <i>A. gracile</i> in the phytoplankton. Of the isolated strains, only <i>A. gracile</i> was confirmed to be a producer of STXs by chemical (LC-MS/MS) and genetic (<i>sxt</i>A) methods. Sequencing of the phycocyanin intergenic spacer and flanking regions (<i>cpc</i>BA) revealed that <i>A. gracile</i> formed a genetically homogenous group. Only trace amounts of ANTX-a were detected in field samples (up to 0.31 µg l^–1 in Lake Širvys). CYN was detected in neither the bloom samples nor in the isolated strains.