Molecular and Chemical Analyses of Cyanobacterial Blooms in Tropical Lagoons from Southeast Brazil

Abstract

The genetic diversity and the potential toxicity of bloom-forming cyanobacteria were studied in four lagoons located in the state of Sao Paulo (Campinas, Limeira and Piracicaba cities). Bloom samples were collected on the water surface and cyanobacterial communities were evaluated using DGGE fingerprinting and 16S rDNA clone library. The amplification of genes encoding secondary metabolites such as microcystin ( mcy ), anatoxin ( ana ), cylindrospermopsin ( cyr ), saxitoxin ( sxt ), cyanopeptolin ( mcn ) and aeruginosin ( aer ) was performed and their production analyzed by LC-MS. The comparison of DGGE banding pattern among the different water samples suggested that some operational taxonomic units (OTUs) in these locations were predominant over others. The 16S rDNA clone libraries sequences matched with nine different known cyanobacterial genera available in NCBI, identified as Anabaena , Brasilonema , Cylindrospermopsis , Limnococcus , Microcystis , Nostoc , Pseudanabaena , Synechococcus and Woronichinia . The lagoons ESALQ2, Taquaral and Limeira had more than 80% of the cyanobacterial community assigned to the genus Microcystis . Genes encoding aeruginosin, cyanopeptolin and microcystin synthetases and saxitoxin synthase were amplified, and LC-MS/MS confirmed the production of aeruginosin, cyanopeptolin and microcystin. Rapid and sensitive methods for the detection of these secondary metabolites, especially toxins, using chemical and molecular tools together, can be used for a faster diagnostic of toxic cyanobacterial blooms.