RESUMEN
Objective To develop a new method to screen the potential microcystin-producing cyanobacteria in natural waters. Methods Cyanobacteria were cultured and waters samples were analyzed by polymerase chain reaction with special primers for gene of the operon mcyD which encodes a microcystin synthetase combining conserved gene 16S rRNA of alga, subsequently, whose microcystins were detected by ELISA. Results There was a unique amplified product of approximately 870 bp in microcystin-producing blue-green alga and water samples, but no target band in non-toxic strains and samples. Conclusion It is feasible to use the molecular biological method used mcyD as the microcystin molecular biomarker to screen microcystin-producing cyanobacteria in natural water.