Molecular approaches to detect cyanobacteria and their microcystins producing genotypes in Billings and Guarapiranga reservoirs, São Paulo, Brazil / Abordagens moleculares para detectar cianobactérias e seus genótipos produtores de microcistinas presentes nas represas Billings e Guarapiranga, São Paulo, Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Cyanobacterial blooms in water reservoirs used for human consumption are frequent nowadays and are usually attributed to the increasing water eutrophization. In recent years, the appearance of toxin-producing cyanobacterial strains has concerned managers of water quality since these toxins represent a public health risk. Early detection of the presence of toxic strains in these reservoirs is essential for the success of bloom control corrective actions. In the present work, cyanobacterial diversity was evaluated in several sites of Billings and Guarapiranga reservoirs using DGGE (denaturing gradient gel eletrophoresis) and/or mini-library constructions of both 16S rRNA gene and phycocyanin intergenic spacer (PC-IGS) region amplicons. The DGGE, using CYA359F/CYA781R primers, specific for cyanobacterial 16S rRNA gene, showed the presence of these organisms in the eleven water samples analyzed. Microcystis aeruginosa (identities of 94-97%), Geitlerinema (identity of 89%) and Synechococcus (identity of 89%) were identified. The mini-library constructed with 16S rRNA amplicons obtained using 27F1/1494Rc primers produced sequences of another group of bacteria (Actinobacteria), indicating the unespecificity of these primers. However, the mini-library constructed with PC-IGS amplicons obtained using PCβF/PCαR primers, generated cyanobacterial sequences only. In this mini-library several Microcystis aeruginosa strains (identities of 98-100%) and Anabaena (identity of 89%) were identified. These two cyanobacterial genera known to produce microcystins were detected in a water sample containing a high concentration of this toxin (23.49 g/L). The OMETF/OMETR primers were designed to amplify a small and variable region of the N-methyltransferase domain of mcyA gene and were tested in thirteen cyanobacterial strains isolated from Billings and Guarapiranga reservoirs. Sequences generated with these primers were successfully isolated, cloned and sequenced in two control species (M. aeruginosa NPJB1 and M. panniformis SPC702) and in two isolates from these reservoirs (M. aeruginosa SPC777 and M. protocystis SPC697). The amplification of this region of mcyA using cultured cyanobacteria DNAs allowed the identification of Microcystis strains with the potential to produce microcystin toxin. This technique, after it is well established for cultured organisms, will provide a basis for better detection of potential microcystin-producing cyanobacterial aquatic communities in natural environments.

ASSUNTO(S)

cloning monitoramento ambiental ciclic peptides peptídeos cíclicos polimorfismo ribosomal rna clonagem rna ribossômico pcr pcr polimorphism environmental monitoring

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