EXPRESSION OF THE GEOSMIN SYNTHASE GENE IN THE CYANOBACTERIUM ANABAENA CIRCINALIS AWQC318¹

Abstract

The occurrence of taste and odor episodes attributed to geosmin continues to trouble water utilities worldwide, and only recently have advances been made in our fundamental understanding of the biochemical and genetic mechanisms responsible for the production of geosmin in microorganisms. For the first time, we have examined the expression of the geosmin synthase gene and corresponding geosmin production by Anabaena circinalis Rabenh. ex Bornet et Flahault AWQC318 under conditions of continuous light illumination and the removal of light as a stimulus and demonstrate that the expression of geosmin synthase appears to be constitutive under these conditions. The decrease in geosmin synthase transcription post maximum cell numbers and stationary phase suggests that a decrease in isoprenoid synthesis may occur before a decrease in the transcription of ribosomal units as the process of cell death is initiated.

Genetic Basis for Geosmin Production by the Water Bloom-Forming Cyanobacterium, Anabaena ucrainica

“…Apart from the benthic/periphytic groups represented above, planktonic (bloom-forming) cyanobacterium species are also likely to produce geosmin [2,7]. However, only Giglio et al [14] have analyzed the expression of geosmin synthase in Anabaena circinalis. Further in-depth studies on the genetics of geosmin synthesis from bloom-forming cyanobacteria have yet to be conducted.…”

2-Methylisoborneol production characteristics of Pseudanabaena sp. FACHB 1277 isolated from Xionghe Reservoir, China

“…2-MIB is a methylated monoterpene alcohol (Bentley and Meganathan 1982). Geranyl diphosphate 2-methyltransferase (GPPMT) catalyzes the monoterpene precursor GPP to 2-methyl-GPP, and then MIB synthase (MIBS) catalyzes the cyclization of 2-methyl-GPP to 2-MIB in cyanobacteria (Giglio et al 2011). The only study on culture temperature affecting 2-MIB production by Kakimoto et al (2014) using P. galeata showed that the expression levels of the genes encoding GPPMT and MIBS decreased at 4°C and increased at 30°C, compared with at 20°C.…”

“…The odor threshold concentrations (OTCs) in water have been reported to be 6.3-15.0 ng L −1 for 2-MIB and 1.3-4.0 ng L −1 for geosmin, respectively (Watson 2004;Wert et al 2014). Despite neither 2-MIB nor geosmin having any known adverse biological and pathological effects, the offensive odor and taste of these compounds may lead to psychosomatic effects, such as headaches, stress, or stomach upsets (Young et al 1996;Lauderdale et al 2004;Giglio et al 2011). 2-MIB (1,2,7,7-tetramethyl-exo-bicyclo[2,2,1]heptan-2-ol), an alicyclic tertiary alcohol, is a crystalline solid with a strong musty odor, which was first isolated from three Streptomyces and one Actinomadura species by Gerber (Gerber 1969;Newcombe et al 2002).…”

Elucidation of Taste- and Odor-Producing Bacteria and Toxigenic Cyanobacteria in a Midwestern Drinking Water Supply Reservoir by Shotgun Metagenomic Analysis

“…Although studies have described primer sets intended to be "general" or "universal" across all or a subset of organisms, by comparing shotgun metagenome read sets to published primer sets, primer-template mismatches are often observed. In this study, a number of heterogeneities were observed between the assembled Cheney geosmin synthase and 15 previously published primers (13,(48)(49)(50) designed to amplify geosmin synthases from cyanobacteria (see Table S3 in the supplemental material). The number of mismatches ranged from 0 to 7 (mean, 2.14), with the 3139F and 3245R primer set developed by Tsao and colleagues (50) being the only perfectly matching set.…”

“…We acknowledge the possibility that reverse transcriptase real-time PCR assays measuring geosmin synthase expression could provide better estimates of geosmin concentrations than the DNA-based assays we used; however, at least one study suggests that geoA expression in Anabaena spp. is constitutive (48), indicating that there may be limited value in using RT-qPCR. Additionally, for practical applications such as routine water quality monitoring, DNA-based methods are generally simpler and are therefore considered more appropriate in this context.…”