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 Lin a, * 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 article info Article history: Received 30 July 2013 Received in revised form 6 October 2013 Accepted 10 October 2013 Available online 18 October 2013 Keywords: Anabaena circinalis Geosmin synthesis gene Monitoring Quantitative PCR Reservoir abstract 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  10 1 to 5  10 5 copies mL 1 , with a high correlation coefficient (R 2 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 tech- niques 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 pro- vide water utilities with the ability to properly characterize a taste and odor episode and choose appropriate management and treatment options. ª 2013 Elsevier Ltd. All rights reserved. 1. Introduction Taste and odor (T&O) problems in drinking water have caused concerns and complaints about water quality worldwide. Although no reports provide direct evidence of adverse health effects from off-flavors produced by microbes, the T&O com- pounds create problems for water quality management because people often interpret off-flavors as evidence that the water is unsafe to drink (Smith et al., 2002). Geosmin is one of the most common off-flavor compounds detected in drinking water and is produced by certain cyanobacteria and actino- mycetes (Ju ¨ ttner and Watson, 2007). Humans have a low odor detection threshold for geosmin, as little as 10 ng L 1 (Cook et al., 2001), and this sensitivity, combined with * Corresponding author. E-mail addresses: tflin@mail.ncku.edu.tw, intf10@gmail.com (T.-F. Lin). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/watres water research 49 (2014) 416 e425 0043-1354/$ e see front matter ª 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.watres.2013.10.028