Volume 29 Issue 5 - July 3, 2015 PDF
Monitoring of geosmin producing Anabaena circinalis using quantitative PCR
Hsiang-Wei Tsao a, Atsuko Michinaka a, Hung-Kai Yen a,b, Steven Giglio c, Peter Hobson c, Paul Monis c, Tsair-Fuh Lina,*
a Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan, ROC
b Department of Biological Science and Technology, Meiho University, Pingtung 91202, Taiwan, ROC
c Australian Water Quality Centre, South Australian Water Corporation, Adelaide, South Australia 5000, Australia
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Geosmin is one of the most commonly observed taste and odor (T&O) compounds present in fresh water bodies. The chemical is a metabolite produced by blue-green algae (now called cyanobacteria) and actinomycetes. It is usually the major cause of many T&O complaints for public water supplies and aquaculture produces. Conventionally, a geosmin associated water-quality issue can be quantified by measuring the odor-producing cyanobacteria, using microscopy enumeration, and/or by detecting the chemical, using gas chromatograph (GC) equipped with a mass selective detector (MSD). However, these methods are time-consuming for multiple samples and either require experienced personnel or sophisticated instrumentation. Recently, quantitative polymerase chain reaction (qPCR) based bio-molecular methods have been developed to detect the genes involved in geosmin synthesis for cyanobacteria. However, no field data are available for the monitoring of geosmin-producing cyanobacteria in fresh water reservoirs. Therefore, the aim of this study is to develop an approach to quantify geosmin producing cyanobacteria using qPCR method and apply the approach in the monitoring of reservoir water quality.

Two primer sets to target the geosmin producing genes were first designed and tested against 21 geosmin and non-geosmin producer cyanobacteria species isolated from Australia and Taiwan. After validation, the primer sets were further applied in the monitoring of an Anabaena circinalis associated geosmin episode in Myponga Reservoir, South Australia. During one month of monitoring, 35 samples were collected for 5 sampling locations in the reservoir. Good correlations were observed for the analytical results of cell counts by microscope, geosmin gene copies by qPCR, and geosmin concentration by GC/MSD. The results suggest that the qPCR based approach may be a good alternative method to quantify geosmin producers and geosmin concentrations for reservoir water samples. Compared with conventional chemical analysis and microscopic enumeration, the qPCR approach offers a rapid method for detection of geosmin-producing A. circinalis. In facing with a T&O episode caused by geosmin, the approach may allow water agencies to better and faster characterize their source water, so that appropriate response processes can be selected.
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