Geosmin is one of the most commonly detected off-flavor chemicals present in reservoirs
and drinking water systems. Quantitative real-time PCR (qPCR) is useful for quantifying
geosmin-producers by focusing on the gene encoding geosmin synthase, which is
responsible for geosmin synthesis. In this study, several primers and probes were designed
and evaluated to detect the geosmin synthase gene in cyanobacteria. The specificity of
primer and probe sets was tested using 21 strains of laboratory cultured cyanobacteria
isolated from surface waters in Australia (18) and Taiwan (2), including 6 strains with
geosmin producing ability. The results showed that the primers designed in this study
could successfully detect all geosmin producing strains tested. The selected primers were
used in a qPCR assay, and the calibration curves were linear from 5 101 to
5 105 copies mL1, with a high correlation coefficient (R2 ¼ 0.999). This method was then
applied to analyze samples taken from Myponga Reservoir, South Australia, during a
cyanobacterial bloom event. The results showed good correlations between qPCR techniques
and traditional methods, including cell counts determined by microscopy and
geosmin concentration measured using gas chromatography (GC) coupled with a mass
selective detector (MSD). Results demonstrate that qPCR could be used for tracking
geosmin-producing cyanobacteria in drinking water reservoirs. The qPCR assay may provide
water utilities with the ability to properly characterize a taste and odor episode and
choose appropriate management and treatment options.
