QUANTIFICATION OF TOXIC CYANOBACTERIA IN WATER BY USE OF COMPETITIVE PCR FOLLOWED BY SEQUENCE-SPECIFIC LABELING OF OLIGONUCLEOTIDE PROBES

A complete nucleic-acid-based assay which consists of sample preparati on, DNA amplification, and chromogenic detection was developed for qua ntifying potential toxin-producing cyanobacteria of interest to the pu blic. The sample preparation strategy involves the same solid phase fo r cell concentration and DNA purification. For the detection step, we used a combination of competitive PCR amplification, sequence-specific labeling of oligonucleotide probes, hybridization of the labeled olig onucleotides to immobilized complements and, finally, chromogenic dete ction, The complete assay was tested,vith water containing toxin-produ cing cyanobacteria belonging to the genus Microcystis. A detection lim it of 100 cells/ml and a quantitative range of more than 3 orders of m agnitude were obtained, This approach can easily be adapted to a wide range of bacterial species and has the potential for simultaneous dete ction and quantitation of several different target organisms by a sing le assay.