Establishment of quantitative PCR methods for the quantification of geosmin-producing potential and Anabaena sp. in freshwater systems

qPCR-Based Monitoring of 2-Methylisoborneol/Geosmin-Producing Cyanobacteria in Drinking Water Reservoirs in South Korea

Cyanobacteria can exist in water resources and produce odorants. 2-Methylisoborneol (2-MIB) and geosmin are the main odorant compounds affecting the drinking water quality in reservoirs. In this study, encoding genes 2-MIB (mic, monoterpene cyclase) and geosmin (geo, putative geosmin synthase) were investigated using newly developed primers for quantitative PCR (qPCR). Gene copy numbers were compared to 2-MIB/geosmin concentrations and cyanobacterial cell abundance. Samples were collected between July and October 2020, from four drinking water sites in South Korea. The results showed similar trends in three parameters, although the changes in the 2-MIB/geosmin concentrations followed the changes in the mic/geo copy numbers more closely than the cyanobacterial cell abundances. The number of odorant gene copies decreased from upstream to downstream. Regression analysis revealed a strong positive linear correlation between gene copy number and odorant concentration for mic (R2 = 0.8478) and geo (R2 = 0.601). In the analysis of several environmental parameters, only water temperature was positively correlated with both mic and geo. Our results demonstrated the feasibility of monitoring 2-MIB/geosmin occurrence using qPCR of their respective synthase genes. Odorant-producing, gene-based qPCR monitoring studies may contribute to improving drinking water quality management.

The importance of nutrient ratios in determining elevations in geosmin synthase (geoA) and 2-MIB cyclase (mic) resulting in taste and odour events

Geosmin synthase (geoA) and 2-MIB cyclase (mic) are key biosynthetic genes responsible for the production of taste and odour (T&O) compounds, geosmin and 2-MIB. These T&O compounds are becoming an increasing global problem for drinking water supplies. It is thought that geosmin and 2-MIB may be linked to, or exacerbated by, a variety of different environmental and nutrient triggers. However, to the best of our knowledge, no studies to date have evaluated the combined effects of seasonality, temperature, and nutrient concentrations on geoA and mic copy numbers in conjunction with T&O concentrations. In this study, environmental triggers behind geosmin and 2-MIB production were investigated in nine reservoirs across Wales, U.K. between July 2019 - August 2020. The abundance of geoA and mic were quantified through quantitative Polymerase Chain Reaction (qPCR). Temporal changes in geoA and geosmin concentrations revealed geoA to be an indicator of monthly geosmin concentrations, although only when geosmin concentrations exceeded 100 ng L-1. Model analysis of a reservoir with elevated geosmin concentrations revealed geoA to be significantly associated with mean temperature (p < 0.001) and the nutrients dissolved reactive silicate (p < 0.001), dissolved iron (p < 0.001), total inorganic nitrogen to phosphorous ratio (TIN:TP) (p < 0.001) and ammonium to nitrate ratio (NH4+:NO3-) (p < 0.001). Sulphate also demonstrated a significant positive linear relationship with geoA (p < 0.001). For mic analysis, NH4+:NO3- was significantly associated with mic (p < 0.05) and an association with dissolved reactive silicate was also observed (p = 0.084). Within this study we also report extreme variance in gene copy numbers between the study seasons. No consistent relationship could be determined for mic copy numbers mL-1 and 2-MIB (ng L-1). The findings from this study indicate that TIN:TP and NH4+:NO3- serve as good predictors for elevated geoA and mic, along with negative linear relationships observed for mean temperature and dissolved reactive silicate. Overall, our findings demonstrate the importance of nutrient concentrations, nutrient ratios and temperature for evidence based predictive capacity of taste and odour events in drinking water reservoirs.

Undesirable odour substances (geosmin and 2-methylisoborneol) in water environment: Sources, impacts and removal strategies

Off-flavours in fish products generated from recirculating aquaculture systems (RAS) are a major problem in the fish farming industry affecting the market demand and prices. A particular concern is the muddy or musty odour and taste in fish due to the presence of secondary metabolites geosmin and 2-methylisoborneol (2-MIB), produced by actinobacteria (mainly Streptomyces), myxobacteria and cyanobacteria. Off-flavours have deteriorated the quality of fish, rendering their products unfit for human consumption. The process of odour removal requires purification for several days to weeks in clean water; thus this leads to additional production costs. Geosmin and 2-MIB, detected at extremely low odour thresholds, are the most widespread off-flavour metabolites in aquaculture, entering through fish gills and accumulating in the fish adipose tissues. In this review, we aimed to determine the diversity and identity of geosmin- and 2-MIB-producing bacteria in aquaculture and provide possible strategies for their elimination.

Evaluation of the MIB-producing potential based on real-time qPCR in drinking water reservoirs

Cyanobacteria release 2-methylisoborneol (MIB) as a secondary metabolite. Here, we propose a reverse transcription quantitative real-time PCR (RT-qPCR) based method to evaluate the MIB-producing potential in source water by detecting the MIB-synthesis gene (mic). A MIBQSF/R primer set was designed based on 35 mic gene sequences obtained from 12 pure-cultured MIB-producing strains and 23 sequences from the NCBI database. This primer set successfully identified all known 43 MIB-producing cyanobacterial strains (12 from this study and 31 from the NCBI database), belonging to different genera, showing a wider coverage than previous primer sets. The efficiency of the method was proved by the amplification efficiency (E = 91.23%), R² of the standard curve (0.999), the limit of detection (LOD, 5.7 fg μL^-1), and the limit of quantification (LOQ, 1.86 × 10⁴ gene copies μL^-1). Further, the method was verified by the correlation between the mic gene abundance and MIB concentration 50 field samples from different reservoirs (R² = 0.614, p < 0.001) and one reservoir (R² = 0.752, p < 0.001), suggesting its potential as an alternative warning tool to evaluate the risk of MIB problems in source water.

Temperature affects growth, geosmin/2-methylisoborneol production, and gene expression in two cyanobacterial species

Cyanobacterial blooms accompanied by taste and odor (T&O) compounds affect the recreational function and safe use of drinking water. Geosmin and 2-methylisoborneol (2-MIB) are the most common T&O compounds. In this study, we investigated the effect of temperature on geosmin and 2-MIB production in Dolichospermum smithii and Pseudanabaena foetida var. intermedia. More specifically, transcription of one geosmin synthase gene (geoA) and two 2-MIB synthase genes (mtf and mtc) was explored. Of the three temperatures (15, 25, and 35 °C) tested, the maximum Chl-a content was determined at 25 °C in both D. smithii and P. foetida var. intermedia. The maximum total geosmin concentration (19.82 μg/L) produced by D. smithii was detected at 25 °C. The total 2-MIB concentration (82.5 μg/L) produced by P. foetida var. intermedia was the highest at 35 °C. Besides, the lowest Chl-a content and minimum geosmin/2-MIB concentration were observed at 15 °C. There was a good positive correlation between geosmin/2-MIB concentration and Chl-a content. The expression levels of the geoA, mtf, and mtc genes at 15 °C were significantly higher than those at 25 and 35 °C. The transcription of the mtf and mtc genes in P. foetida var. intermedia was higher at 35 °C than at 25 °C. The results highlight unfavorable temperature can increase the potential of geosmin/2-MIB synthesis from the gene expression level in cyanobacteria. This study could provide basic knowledge of geosmin/2-MIB production by cyanobacteria for better understanding and management of T&O problems in drinking water.

Ecological niche and in-situ control of MIB producers in source water

Odor problems in source water caused by 2-methylisoborneol (MIB) have been a common issue in China recently, posing a high risk to drinking water safety. The earthy-musty odorant MIB has an extremely low odor threshold (4-16 ng/L) and is hard to remove via conventional processes in drinking water plants (DWP), and therefore could easily provoke complaints from consumers. This compound is produced by a group of filamentous cyanobacteria, mainly belonging to Oscillatoriales. Different from the well-studied surface-blooming Microcystis, filamentous cyanobacteria have specific niche characteristics that allow them to stay at a subsurface or deep layer in the water column. The underwater bloom of these MIB producers is therefore passively determined by the underwater light availability, which is governed by the cell density of surface scum. This suggests that drinking water reservoirs with relatively low nutrient contents are not able to support surface blooms, but are a fairly good fit to the specialized ecological niche of filamentous cyanobacteria; this could explain the widespread odor problems in source water. At present, MIB is mainly treated in DWP using advanced treatment processes and/or activated carbon, but these post-treatment methods have high cost, and not able to deal with water containing high MIB concentrations. Thus, in situ control of MIB producers in source water is an effective complement and is desirable. Lowering the underwater light availability is a possible measure to control MIB producers according to their niche characteristics, which can be obtained by either changing the water level or other measures.

Impact of water quality parameters on geosmin levels and geosmin producers in European recirculating aquaculture systems

AIMS

Geosmin is associated with off-flavour problems in recirculating aquaculture systems (RAS) and represents an economic problem for the aquaculture industry. This study aims at investigating factors influencing the composition of the bacterial microbiota, in particular the presence of geosmin producers and the environmental and farming factors favouring geosmin accumulation.

METHODS AND RESULTS

Several water quality parameters were correlated to the composition of the microbiota with special emphasis on the presence of geosmin producers within 26 different RAS from four European countries. Three novel groups of geosmin-producing bacteria were quantified to identify potential correlations with geosmin concentration.

CONCLUSIONS

The microbiome differed significantly between systems. However, phosphate levels, calcium levels and redox potential correlated to geosmin concentration in the water and the presence of the Actinomycetales geosmin-producers but not with the presence of other groups of geosmin-producing bacteria. Oxygen levels and conductivity were found to negatively correlate with geosmin concentration. A large proportion of the detected geosmin producers represented novel taxonomic groups not previously linked with this activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results improve our understanding of the diversity of microbiota in RAS and the water quality parameters favouring the populations of geosmin-producing bacteria and the production of geosmin.

Quantitative PCR based detection system for cyanobacterial geosmin/2-methylisoborneol (2-MIB) events in drinking water sources: Current status and challenges

Taste and odor (T&O) are an important issue in drinking water, aquaculture, recreation and a few other associated industries, and cyanobacteria-relevant geosmin and 2-methylisoborneol (2-MIB) are the two most commonly detected T&O compounds worldwide. A rise in the cyanobacterial blooms and associated geosmin/2-MIB episodes due to anthropogenic activities as well as climate change has led to global concerns for drinking water quality. The increasing awareness for the safe drinking, aquaculture or recreational water systems has boost the demand for rapid, robust, on-site early detection and monitoring system for cyanobacterial geosmin/2-MIB events. In past years, research has indicated quantitative PCR (qPCR) as one of the promising tools for detection of geosmin/2-MIB episodes. It offers advantages of detecting the source organism even at very low concentrations, distinction of odor-producing cyanobacterial strains from non-producers and evaluation of odor producing potential of the cyanobacteria at much faster rates compared to conventional techniques.The present review aims at examining the current status of developed qPCR primers and probes in identifying and detecting the cyanobacterial blooms along with geosmin/2-MIB events. Among the more than 100 articles about cyanobacteria associated geosmin/2-MIB in drinking water systems published after 1990, limited reports (approx. 10 each for geosmin and 2-MIB) focused on qPCR detection and its application in the field. Based on the review of literature, a comprehensive open access global cyanobacterial geosmin/2-MIB events database (CyanoGM Explorer) is curated. It acts as a single platform to access updated information related to origin and geographical distribution of geosmin/2-MIB events, cyanobacterial producers, frequency, and techniques associated with the monitoring of the events. Although a total of 132 cyanobacterial strains from 21 genera and 72 cyanobacterial strains from 13 genera have been reported for geosmin and 2-MIB production, respectively, only 58 geosmin and 28 2-MIB synthesis regions have been assembled in the NCBI database. Based on the identity, geosmin sequences were found to be more diverse in the geosmin synthase conserved/primer design region, compared to 2-MIB synthesis region, hindering the design of universal primers/probes. Emerging technologies such as the bioelectronic nose, Surface Enhanced Raman Scattering (SERS), and nanopore sequencing are discussed for future applications in early on-site detection of geosmin/2-MIB and producers. In the end, the paper also highlights various challenges in applying qPCR as a universal system of monitoring and development of response system for geosmin/2-MIB episodes.

The diversity, origin, and evolutionary analysis of geosmin synthase gene in cyanobacteria

The sesquiterpene geosmin, mainly originating from cyanobacteria, is considered one of the problematic odor compounds responsible for unpleasant-tasting and -smelling water episodes in freshwater supplies. The biochemistry and genetics of geosmin synthesis in cyanobacteria is well-elucidated and the geosmin synthase gene (geo) has been cloned and characterized in recent years. However, understanding the diversity, origin, and evolution of geo has been hindered by the limited availability of geo sequences to date. On the basis of the cloned geo sequences from16 filamentous geosmin-producing cyanobacterial species, representing 11 genera in Nostocales and Oscillatoriales, the diversity and evolution of geo in cyanobacteria was systematically analyzed in this study. Homologous alignment revealed that geo is highly conserved among the examined cyanobacterial species, with DNA sequence identities >0.72. Phylogenetic reconstruction and codon bias analysis based on geo suggest that cyanobacterial geo form a monophyletic branch with a common origin and ancestor for cyanobacteria, actinomycetes, and myxobacteria. The global ratio of nonsynonymous/synonymous nucleotide substitutions (dN/dS) was 0.125, which is substantially <1 and indicates strong purifying selection in the evolution of cyanobacterial geo. To add to further interest, horizontal gene transfer of cyanobacterial geo in evolutionary history was confirmed by the discovery of an incongruent coevolutionary relationship between geo and housekeeping genes 16S rDNA and rpoC. The present study enhances the fundamental understanding of cyanobacterial geo in diversity and evolution, and sheds light on the development of molecular assays for detection and molecular ecology research of geosmin-producing cyanobacteria.

Identification of geosmin biosynthetic gene in geosmin-producing colonial cyanobacteria Coelosphaerium sp. and isolation of geosmin non-producing Coelosphaerium sp. from brackish Lake Shinji in Japan

Geosmin is an earthy-muddy smelling compound produced in aquatic ecosystems by microorganisms including cyanobacteria. An increase in geosmin levels affecting the local fishery occurred in May 2007 in Lake Shinji, Japan, and geosmin-producing colonial cyanobacterium, Coelosphaerium sp. G2, was isolated from a water sample from the lake and identified. Cyanobacteria Coelosphaerium sp. is commonly found in Lake Shinji; however, prior to 2007, earthy-muddy odors were not a frequent issue. Further, there was no information regarding the geosmin biosynthetic gene in colonial cyanobacteria. Here, the geosmin biosynthetic gene (geoA) in strain G2 was identified and its nucleotide sequence was determined. It was found that geoA had 79% and 78% identity with geoA from filamentous geosmin-producing cyanobacteria Fischerella sp. PCC 9431 and geoA2 from Phormidium sp. P2r, respectively. The deduced amino acid sequence of GeoA consisted of two domains that were annotated as terpene cyclase. In 2015, geosmin non-producing Coelosphaerium sp. S3C5 was isolated from Lake Shinji and identified by morphological and genetic analyses. There was no difference in morphology or nucleotide sequences of 16S rRNA and 16S-23S internal transcribed spacer (ITS) between geosmin-producing and non-producing strains, which are therefore closely related and can exist in Lake Shinji. Distinguishing the two strains by observation under a microscope and sequencing of 16S rRNA and 16S-23S ITS have proven difficult. Inconsistency between the appearance of Coelosphaerium cells and the detection of the odor in water samples could therefore be attributed to dominance by the geosmin-producing strain or the non-producing strain. The increase in earthy smell is assumed to be caused by an increase in the geosmin-producing strain in Lake Shinji. Genetic analysis of geoA in Coelosphaerium sp. and the relative abundances of geosmin-producing and non-producing Coelosphaerium strains in Lake Shinji can be used to mitigate the economic damages caused by geosmin. Development of a molecular method to monitor the geosmin-producing strain in water ecosystems is equally important to alleviate the earthy smell caused by this particular strain.

An improved method for PCR-based detection and routine monitoring of geosmin-producing cyanobacterial blooms

Production of taste and odour (T/O) compounds, principally geosmin, by complex cyanobacterial blooms is a major water quality issue globally. Control of these cyanobacteria imposes a significant cost on water producing and dependent industries, and requires routine monitoring and management. Classic monitoring methods, including microscopy and direct chemical analysis, lack sensitivity, are laborious, expensive or cannot reliably identify the source of geosmin production. Polymerase Chain Reaction (PCR) based tools targeting the geosmin synthase gene (geoA) provide a novel tool for routine monitoring. However, geoA is variable at the nucleotide level and potential geosmin producers represent a broad taxonomic distribution, such that multiple PCR primers with distinct amplification protocols are needed to target all potential sources of this important T/O compound. Development of novel primers is hindered by a lack of sequence data and limited field and laboratory data on geosmin producers prevents prioritizing taxa for PCR testing. Here we performed a genetic screen of 253 bloom samples from Victoria, Australia using each existing PCR protocol targeting geoA. We detected Dolichospermum ucrainicum as the major geosmin producer (87% of sequenced samples) along with 3 unknown geoA sequence types. Using these data, we designed a novel, short amplicon, PCR protocol utilising a single standardised primer pair, capable of amplifying all geoA positive samples in our study, as well as a Nostoc punctiforme positive control. This single protocol geoA PCR can further be tested on other geosmin producers and will simplify routine monitoring of T/O producing cyanobacteria.

The role of algae and cyanobacteria in the production and release of odorants in water

This review covers literatures pertaining to algal and cyanobacterial odor problems that have been published over the last five decades. Proper evaluation of algal and cyanobacterial odors may help establish removal strategies for hazardous metabolites while enhancing the recyclability of water. A bloom of microalgae is a sign of an anthropogenic disturbance in aquatic systems and can lead to diverse changes in ecosystems along with increased production of odorants. In general, because algal and cyanobacterial odors vary in chemistry and intensity according to blooming pattern, it is necessary to learn more about the related factors and processes (e.g., changes due to differences in taxa). This necessitates systematic and transdisciplinary approaches that require the cooperation of chemists, biologists, engineers, and policy makers.

An overview of diversity, occurrence, genetics and toxin production of bloom-forming Dolichospermum (Anabaena) species

The new genus name Dolichospermum, for most of the planktonic former members of the genus Anabaena, is one of the most ubiquitous bloom-forming cyanobacterial genera. Its dominance and persistence have increased in recent years, due to eutrophication from anthropogenic activities and global climate change. Blooms of Dolichospermum species, with their production of secondary metabolites that commonly include toxins, present a worldwide threat to environmental and public health. In this review, recent advances of the genus Dolichospermum are summarized, including taxonomy, genetics, bloom occurrence, and production of toxin and taste-and-odor compounds. The recent and continuing acquisition of genome sequences is ushering in new methods for monitoring and understanding the factors regulating bloom dynamics.

Biochemistry and genetics of taste- and odor-producing cyanobacteria

Cyanobacteria are one of the principal sources of volatile organic compounds (VOCs) which cause offensive taste and odor (T&O) in drinking and recreational water, fish, shellfish and other seafood. Although non-toxic to humans, these T&O compounds severely undermine public trust in these commodities, resulting in substantial costs in treatment, and lost revenue to drinking water, aquaculture, food and beverage and tourist/hospitality industries. Mitigation and control have been hindered by the complexity of the communities and processes which produce and modify T&O events, making it difficult to source-track the major producer(s) and the factors governing VOC production and fate. Over the past decade, however, advances in bioinformatics, enzymology, and applied detection technologies have greatly enhanced our understanding of the pathways, the enzymes and the genetic coding for some of the most problematic VOCs produced by cyanobacteria. This has led to the development of tools for rapid and sensitive detection and monitoring for the VOC production at source, and provided the basis for further diagnostics of endogenous and exogenous controls. This review provides an overview of current knowledge of the major cyanobacterial VOCs, the producers, the biochemistry and the genetics and highlight the current applications and further research needs in this area.

Isolation and characterization of a new reported cyanobacterium Leptolyngbya bijugata coproducing odorous geosmin and 2-methylisoborneol

The earthy-musty compounds geosmin and 2-methylisoborneol (MIB) produced by cyanobacteria are considered as the main biological causes of off-flavor events, especially in aquatic ecosystems. More than 50 filamentous cyanobacteria species have been documented as geosmin or MIB producers; however, little is known about the species coproducing these two metabolites. In this study, an epiphytic sample was collected from a river in Hubei, China. Three isolated strains (A2, B2, and B4) producing earthy odors were successfully isolated and identified as the cyanobacterium Leptolyngbya bijugata Anagnostidis et Komárek 1988 based on morphology and 16S rDNA sequences. Gas chromatography analysis confirmed that the isolated L. bijugata strains were geosmin and MIB coproducers, with accumulation ranging from 13.6 to 22.4 and 12.3 to 57.5 μg L(-1), respectively. The partial fragments of geosmin and MIB synthesis genes in the L. bijugata strains were cloned and sequenced. Further sequences and phylogenetic analysis indicated the high conservation and a common origin of these genes in cyanobacteria. This study is the first to report and characterize the coproduction of geosmin and MIB by L. bijugata, representing a new source for potential risk of off-flavor events.

MIB-producing cyanobacteria (Planktothrix sp.) in a drinking water reservoir: distribution and odor producing potential

The production of odorant 2-methylisoborneol (MIB) in water bodies by Planktothrix sp. have not been understood very well. Through a four-year investigation in Miyun Reservoir, a huge mesotrophic drinking water reservoir known to have the MIB episodes, we found that the Planktothrix sp. bloomed during September and October causing the high levels of MIB in the reservoir. The concentration of MIB and the biomass of MIB-producing cyanobacteria Planktothrix were measured (n = 887) at different sites and depths during different seasons. The results indicated that the shallow region of the reservoir is the major habitat for Planktothrix sp. due to that the light is able to penetrate down to the relatively high concentrations of nutrients close to the sediments. Quantile regression analysis between Planktothrix biomass and MIB concentration shows that the risk of MIB exceeding the odor threshold (15 ng L⁻¹) in water was as high as 90% when the Planktothrix density was more than 4.0 × 10⁵ cells L⁻¹, while the risk was reduced to 10% when the Planktothrix density remained below 1.6 × 10⁴ cells L⁻¹. This study will improve the understanding of the environmental behaviors of Planktothrix sp., and can provide useful information for better management of drinking water lakes/reservoirs experiencing the taste and odor (T&O) problems caused by deep living cyanobacterial species.

Identification of geosmin and 2-methylisoborneol in cyanobacteria and molecular detection methods for the producers of these compounds

Geosmin and 2-methylisoborneol (MIB) are muddy/earthy off-flavor metabolites produced by a range of bacteria. Cyanobacteria are the major producers of the volatile metabolites geosmin and MIB which produce taste and odor problems in drinking water and fish worldwide. Here we detected geosmin and MIB by studying 100 cyanobacteria strains using solid phase microextraction gas chromatography mass spectrometry (SPME GC-MS). A total of 21 geosmin producers were identified from six cyanobacteria genera. Two of the geosmin producers also produced MIB. A PCR protocol for the detection of geoA and MIB synthase genes involved in the biosynthesis of geosmin and MIB was developed. The geoA and MIB synthase genes were detected in all strains shown to produce geosmin and MIB, respectively. Cyanobacterial geoA and MIB synthase sequences showed homology to terpene synthases genes of actinobacteria and proteobacteria. Additional off-flavor compounds, nor-carotenoids β-ionone and β-cyclocitral, were found from 55 strains among the 100 cyanobacterial strains studied; β-ionone was present in 45 and β-cyclocitral in 10 strains. Six of the cyanobacteria which contain off-flavor compounds also produced toxins, anatoxin-a or microcystins. The molecular method developed is a useful tool in monitoring potential cyanobacterial producers of geosmin and MIB.

Monitoring of geosmin producing Anabaena circinalis using quantitative PCR

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) = 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.