Brazil has a history of blooms and contamination of freshwater systems by cyanobacterial toxins. The monitoring relevance of toxins from cyanobacteria in reservoirs for public supply is notorious given its high toxicity to mammals, included humans beings. The most recurrent toxins in Brazilian water bodies are microcystins (MC). However, the recent record of cylindrospermopsin (CyN) in northeastern Brazil, Pernambuco state, alerts us to the possibility that this could be escalating. This study reports occurrence of MC and CYN, quantified with ELISA, in 10 reservoirs, devoted to public drinking supply in northeastern Brazil. The composition and quantification of the cyanobacteria community associated with these water bodies is also presented. From 23 samples investigated for the presence of MC, and CyN, 22 and 8 out were positive, respectively. Considering the similarity of the cyanobacteria communities found in reservoirs from Pernambuco, including toxin-producing species associated to MC and CyN, we suggest that geographic spreading can be favored by these factors. These issues emphasize the need for increased monitoring of MC and CyN in drinking supply reservoirs in Brazil.

It is reported for the first time in Brazil and South America the presence of cylindrospermopsin (CYN) in water supply reservoirs. CYN is a powerful hepatotoxic alkaloid implicated in outbreaks of human sicknesses. We detected CYN in different sources of water in Northeastern Brazil using molecular and immunological techniques. The highest concentrations of toxin occurred in the Jucazinho reservoir with the phytoplankton containing the potentially CYN-producing Cylindrospermopsis raciborskii and Sphaerospermopsis aphanizomenoides (previously known as Aphanizomenon aphanizomenoides). The polyketide synthase (PKS) and peptide synthetase (PS), which are directly related to the ability to produce CYN, were found in all the analyzed samples. The result of the present study emphasizes the need to improve monitoring of CYN in water bodies used for drinking and recreation, in order to avoid exposure of human populations to this toxin.

The aim of this study was to evaluate the use of new oligonucleotide primers (mcyB-F/R, mcyB-F/R-A, and mcyB-F/R-B) designed from Brazilian cyanobacteria for the detection of microcystin-producing genotypes in 27 environmental samples from water reservoirs and 11 strains of Microcystis. Microcystins were found using HPLC in all 11 strains and 19 of the environmental samples. The new oligonucleotide primers amplified fragments of microcystin-producing genes, including the eight environmental samples in which no microcystins were detected by HPLC, but which presented amplified fragments, thereby demonstrating the existence of microcystin-producing genes. The new oligonucleotide primers exhibited better specificity when used with environmental samples and were more reliable in comparison with those described in the literature (mcyB-FAA/RAA and mcyA-Cd/FR), which generate false-negative results. The better performance of these new oligonucleotide primers underline the need for designing molecular markers that are well fitted to the regional biological diversity. As this is a fast predictive technique for determining the presence or absence of microcystins, it could be used either alone or in conjunction with other techniques, such as the screening of samples to be sent for quantitative toxicological analysis using HPLC, thereby reducing monitoring cost and time. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.

Cyanobacterial blooms have become a worldwide concern due to the production of toxins harmful to humans and animals. In Brazil and worldwide, microcystins are the most frequently found cyanotoxin in water bodies. Four important reservoirs in Brazil's Southeast and Northeast regions were sampled to identify the cyanobacteria community and the occurrence of potential toxin-producing species in the country's public supply reservoirs. A total of 14 taxa were identified, 11 of which are known as potential toxin producers. Potentially toxic cyanobacteria were recorded at concentrations above 20,000 cells·mL -1 in all samples from all four reservoirs, thus requiring microcystin monitoring in drinking water according to Brazilian legislation. Although the sample from Mundaú reservoir showed the highest concentration of microcystins in water, it had one of the lowest values of cells·mL -1 , which demonstrates the non-correspondence between these two parameters. This calls into question the existence of a minimum level of potentially toxic cyanobacteria cells to merit the monitoring of microcystins in the treated water from these sources.

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Selection of genes that have not been horizontally transferred for prokaryote phylogenetic inferences is regarded as a challenging task. The markers internal transcribed spacer of ribosomal genes (16S–23S ITS) and phycocyanin intergenic spacer (PC‐IGS), based on the operons of ribosomal and phycocyanin genes respectively, are among the most used markers in cyanobacteria. The region of the ribosomal genes has been considered stable, whereas the phycocyanin operon may have undergone horizontal transfer. To investigate the occurrence of horizontal transfer of PC‐IGS, phylogenetic trees of Geitlerinema and Microcystis strains were generated using PC‐IGS and 16S–23S ITS and compared. Phylogenetic trees based on the two markers were mostly congruent for Geitlerinema and Microcystis, indicating a common evolutionary history among ribosomal and phycocyanin genes with no evidence for horizontal transfer of PC‐IGS. Thus, PC‐IGS is a suitable marker, along with 16S–23S ITS for phylogenetic studies of cyanobacteria.

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Microcystins and cylindrospermopsins molecular markers for the detection of toxic cyanobacteria: a case study of northeastern Brazilian reservoirsThe presence of potentially toxic cyanobacteria in 10 northeastern Brazilian reservoirs used for public water supply was evaluated with molecular markers specific to genes of microcystins (MC) and cylindrospermopsins (CYN). The detection of the MC genes mcyA and mcyB was determined using 3 different primer pairs. Genes of CYN were assessed by PCR amplification of PKS and PS genes. Amplicons of the different cyanotoxin genes were subjected to sequencing. Genes coding for MC (mcyA and/or mcyB) were found in all of the analysed samples. Despite the presence of the mcyB gene and the subsequent immunological detection of MC, the absence of mcyA was observed in several samples. In general, the primers targeting the PKS gene were more specific, while those for the PS gene gave uneven PCR amplification. In addition, the detection of CYN was only possible when the samples were positive for both the PKS and the PS genes. These findings show that, when working with environmental samples, the use of molecular markers for the detection of potentially toxic cyanobacteria may generate variable results, and consideration should be given to possible phytogeographic genetic variations.