Avaliação da produção de toxinas por cianobactérias bentônicas e perifíticas

Abstract

Most of the knowledge about cyanobacteria toxin production is traditionally associated with planktonic cynobacterial blooms. However, some studies have been showing that benthic and periphytic cyanobacterias can produce cyanotoxins. According to this, we aimed to evaluate the production of microcystins and saxitoxins and the yield potential of these toxins through the presence of genes involved in their synthesis in benthic and periphytic cyanobacterias isolated from some sample sites of the Mundaú river basin, Pernambuco, and the Environmental Protection Area of Araripe, Ceará. And due to the difficulty of strains morphological classification, phylogenetic analysis were performed using the 16S rDNA and 16S-23S ITS. The material was sampled in rivers and water supply reservoirs, using micromanipulation tec hniques. We isolated 45 clonal strains of cyanobacteria, which were identified morphologically and genetically. In order to evaluate the toxins production, the strains were cultured in controlled laboratory conditions for obtaining biomass for subsequent extraction and analysis of toxins by HPLC. In a complementary way of the toxins analysis, PCR’s were performed screening for genes involved on microcystins and saxitoxins production. Eight species were identified belonging to the Phormidiaceae, Pseudanabaenaceae and Nostocaceae families. This is the first study in Brazil that shows that strains from the Geitlerinema genus correspond to at least three phylogenetic lineages, which possibly correspond to three distinct species to be subsequently reclassified. The strains that showed one of the genes involved in the cyanotoxins production were analyzed by HPLC and Geitlerinema amphibium, G. lemmermannii, Cylindrospermum stagnale and Phormidium uncinatum were identified as producing one or more saxitoxins variants. Thus, this is the first report of saxitoxins producing for those first three species and the first report in Brazil for P. uncinatum.