title: Quantity of the dinoflagellate sxtA4 gene and cell density correlates with paralytic shellfish toxin production in Alexandrium ostenfeldii blooms.
abstract: Many marine dinoflagellates, including several species of the genus Alexandrium, Gymnodinium catenatum, and Pyrodinium bahamense are known for their capability to produce paralytic shellfish toxins (PST), which can cause severe, most often food-related poisoning. The recent discovery of the first PST biosynthesis genes has laid the foundation for the development of molecular detection methods for monitoring and study of PST-producing dinoflagellates. In this study, a probe-based qPCR method for the detection and quantification of the sxtA4 gene present in Alexandrium spp. and Gymnodinium catenatum was designed. The focus was on Alexandrium ostenfeldii, a species which recurrently forms dense toxic blooms in areas within the Baltic Sea. A consistent, positive correlation between the presence of sxtA4 and PST biosynthesis was observed, and the species was found to maintain PST production with an average of 6 genomic copies of sxtA4. In August 2014, A. ostenfeldii populations were studied for cell densities, PST production, as well as sxtA4 and species-specific LSU copy numbers in Föglö, Åland, Finland, where an exceptionally dense bloom, consisting of 6.3×106cellsL-1, was observed. Cell concentrations, and copy numbers of both of the target genes were positively correlated with total STX, GTX2, and GTX3 concentrations in the environment, the cell density predicting toxin concentrations with the best accuracy (Spearman's ρ=0.93, p<0.01). The results indicated that all A. ostenfeldii cells in the blooms harbored the genetic capability of PST production, making the detection of sxtA4 a good indicator of toxicity.
authors.affiliation: Biotechnology, Department of Biochemistry, University of Turku, Tykistökatu 6 A 6th Floor, FI-20520 Turku, Finland. Electronic address: henna.savela@utu.fi.
authors.forename: Henna
authors.initials: H
authors.lastname: Savela
authors.affiliation: VERIFIN - Finnish Institute for Verification of the Chemical Weapons Convention, Department of Chemistry, P.O. Box 55, FI-00014 University of Helsinki, Finland.
authors.forename: Kirsi
authors.initials: K
authors.lastname: Harju
authors.affiliation: Biochemistry, Faculty of Natural Science and Engineering, Åbo Akademi University, Tykistökatu 6A 3rd Floor, FI-20520 Turku, Finland.
authors.forename: Lisa
authors.initials: L
authors.lastname: Spoof
authors.affiliation: Ecology and Evolution in Microbial model System (EEMiS), Department of Biology and Environmental Science (BoM), Linnæus University, Kalmar 39182, Sweden.
authors.forename: Elin
authors.initials: E
authors.lastname: Lindehoff
authors.affiliation: Biochemistry, Faculty of Natural Science and Engineering, Åbo Akademi University, Tykistökatu 6A 3rd Floor, FI-20520 Turku, Finland.
authors.forename: Jussi
authors.initials: J
authors.lastname: Meriluoto
authors.affiliation: Biotechnology, Department of Biochemistry, University of Turku, Tykistökatu 6 A 6th Floor, FI-20520 Turku, Finland.
authors.forename: Markus
authors.initials: M
authors.lastname: Vehniäinen
authors.affiliation: Marine Research Centre, Finnish Environment Institute, Erik Palménin aukio 1, FI-00560 Helsinki, Finland.
authors.forename: Anke
authors.initials: A
authors.lastname: Kremp
mesh_terms: D004141:Dinoflagellida / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005387:Finland; D011156:Population Density; D060888:Real-Time Polymerase Chain Reaction; D012530:Saxitoxin / Q000235:genetics* / Q000378:metabolism*
chemical_list: D012530:Saxitoxin
keywords: Alexandrium; Dinoflagellate; paralytic shellfish toxin; qPCR; sxtA4