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Alexandrium tamarense

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Uwe John – 1st expert on this subject based on the ideXlab platform

  • Characterization of populations of Alexandrium tamarense by Genotypic and Phenotypic Markers
    , 2020
    Co-Authors: Tilman J. Alpermann, Urban Tillmann, Uwe John, Allan Cembella

    Abstract:

    Dense populations of the mixotrophic dinoflagellate Alexandrium tamarense can be found in coastal temperate waters with an almost globally distribution. In many cases such algal blooms are responsible for paralytic shellfish poisoning (PSP) events, which are mediated by saxitoxin and its derivatives. These toxins are produced by the dinoflagellates and accumulate in the food chain. However, not all populations of Alexandrium tamarense are capable of PSP toxin production. The role of additional biologically active chemical compounds for the development and persistence of plankton blooms by processes such as anti-grazing defence or inhibition of competitors is not yet clarified. In co-incubation experiments such biological interactions can be investigated and the magnitude of the observed effects can be determined. Studying populations from different regions that are more closely or more distantly related can elucidate the evolutionary significance of such properties. In this study, a combination of genotypic makers such as sequences of the 28S rDNA, microsatellites and amplified fragment length polymorphisms (AFLP) proofed to show the relatedness of populations of Alexandrium tamarense with a different degree of resolution. Phenotypic markers such as toxicity and toxin profile composition as well as the expression of the above mentioned allelopathic properties can then be analysed for the correlation with the genotypic markers. The expression of phenotypic characters and their ecological significance can then be seen from an evolutionary biological perspective.

  • SHORT COMMUNICATION Development of specific rRNA probes to distinguish between geographic clades of the Alexandrium tamarense species complex
    , 2020
    Co-Authors: Uwe John, Linda Medlin, Alfred Wegener

    Abstract:

    The globally occurring Alexandrium tamarense/fundyense/catenella species complex consists of toxic and non-toxic strains that are morphologically difficult to distinguish. We developed four specific ribosomal RNA probes that can identify the entire species complex, the strains of the toxic North American clade and the strains of the two non-toxic clades from Western Europe and the Mediterranean Sea by DNA dot blot and fluorescence in situ hybridization. These probes are a first step for the development of an early warning system for the presence of A. tamarense.

  • a molecular and co evolutionary context for grazer induced toxin production in Alexandrium tamarense
    PLOS ONE, 2010
    Co-Authors: Sylke Wohlrab, Morten Hvitfeldt Iversen, Uwe John

    Abstract:

    Marine dinoflagellates of the genus Alexandrium are the proximal source of neurotoxins associated with Paralytic Shellfish Poisoning. The production of these toxins, the toxin biosynthesis and, thus, the cellular toxicity can be influenced by abiotic and biotic factors. There is, however, a lack of substantial evidence concerning the toxins’ ecological function such as grazing defense. Waterborne cues from copepods have been previously found to induce a species-specific increase in toxin content in Alexandrium minutum. However, it remains speculative in which context these species-specific responses evolved and if it occurs in other Alexandrium species as well. In this study we exposed Alexandrium tamarense to three copepod species (Calanus helgolandicus, Acartia clausii, and Oithona similis) and their corresponding cues. We show that the species-specific response towards copepod-cues is not restricted to one Alexandrium species and that co-evolutionary processes might be involved in these responses, thus giving additional evidence for the defensive role of phycotoxins. Through a functional genomic approach we gained insights into the underlying molecular processes which could trigger the different outcomes of these species-specific responses and consequently lead to increased toxin content in Alexandrium tamarense. We propose that the regulation of serine/threonine kinase signaling pathways has a major influence in directing the external stimuli i.e. copepod-cues, into different intracellular cascades and networks in A. tamarense. Our results show that A. tamarense can sense potential predating copepods and respond to the received information by increasing its toxin production. Furthermore, we demonstrate how a functional genomic approach can be used to investigate species interactions within the plankton community.

Linda K. Medlin – 2nd expert on this subject based on the ideXlab platform

  • Six new microsatellite markers for the toxic marine dinoflagellate Alexandrium tamarense
    Molecular Ecology Notes, 2006
    Co-Authors: Tilman J. Alpermann, Uwe John, Linda K. Medlin, Keith J. Edwards, Paul K. Hayes, Katharine M. Evans

    Abstract:

    We report the characterization of six new microsatellite loci for the toxic marine dinoflagellate Alexandrium tamarense (North American ribotype), using 56 isolates from a range of locations. The numbers of alleles per locus ranged from five to nine and gene diversities ranged from 0.041 to 0.722. We tested primers for these six loci on other A. tamarense ribotypes and on other Alexandrium species; the results suggest that the primers are specific to A. tamarense isolates belonging to the North American ribotype.

  • Phylogenetic analysis of selected toxic and non-toxic bacterial strains isolated from the toxic dinoflagellate Alexandrium tamarense
    FEMS Microbiology Ecology, 2006
    Co-Authors: Martina Kopp, Gregory J. Doucette, Masaaki Kodama, Gunnar Gerdts, Christian Schütt, Linda K. Medlin

    Abstract:

    Recent evidence has implicated bacterial involvement in the production of paralytic shellfish poison toxins, which are normally associated with bloom-forming algal species, specifically toxic dinoflagellate algae. Preliminary reports of the identification of toxin-producing bacteria isolated from the toxic marine dinoflagellate Alexandrium tamarense suggested that they belonged to the gamma sub-division of the Proteobacteria, specifically related to the bacterium Moraxella. Digoxigenin-labelled alpha, beta and gamma ribosomal rRNA probes, hybridized to both toxigenic and non-toxigenic bacteria isolated from several strains of Alexandrium tamarense, indicated that the bacteria belonged to the alpha sub-division of the Proteobacteria. Phylogenetic analysis of small subunit ribosomal RNA coding regions confirmed this and provided strong evidence that these bacteria are likely to represent a new genus in that group.

  • development of specific rrna probes to distinguish between geographic clades of the Alexandrium tamarense species complex
    Journal of Plankton Research, 2004
    Co-Authors: Uwe John, Linda K. Medlin, R Groben

    Abstract:

    The globally occurring Alexandrium tamarense/fundyense/catenella species complex consists of toxic and non-toxic strains that are morphologically difficult to distinguish. We developed four specific ribosomal RNA probes that can identify the entire species complex, the strains of the toxic .orth American clade and the strains of the two non-toxic clades from Western Europe and the Mediterranean Sea by DNA dot blot and fluorescence in situ hybridization. These probes are a first step for the development of an early warning system for the presence of A. tamarense.

Yasukatsu Oshima – 3rd expert on this subject based on the ideXlab platform

  • effect of 5 fluoro 2 deoxyuridine on toxin production and cell cycle regulation in marine dinoflagellate Alexandrium tamarense
    Harmful Algae, 2014
    Co-Authors: Motoo Ogawa, Mari Yotsuyamashita, Yasukatsu Oshima

    Abstract:

    Abstract The effect of metabolic inhibitor, 5-fluoro-2′-deoxyuridine (FUdR) on toxin production and the cell cycle of marine dinoflagellate, Alexandrium tamarense, was investigated. Compared to untreated cells, FUdR at 3 μM (p

  • Effect of 5-fluoro-2′-deoxyuridine on toxin production and cell cycle regulation in marine dinoflagellate, Alexandrium tamarense
    Harmful Algae, 2014
    Co-Authors: Motoo Ogawa, Mari Yotsu-yamashita, Yasukatsu Oshima

    Abstract:

    Abstract The effect of metabolic inhibitor, 5-fluoro-2′-deoxyuridine (FUdR) on toxin production and the cell cycle of marine dinoflagellate, Alexandrium tamarense, was investigated. Compared to untreated cells, FUdR at 3 μM (p

  • single cell analysis of paralytic shellfish toxins in Alexandrium tamarense by hplc with post column fluorescent derivatization
    Harmful Algae, 2013
    Co-Authors: Ryoko Ozeki, Mari Yotsuyamashita, Yasukatsu Oshima

    Abstract:

    Abstract We developed a methodology for analyzing the C-toxin (C2) content in single Alexandrium tamarense cells; this method was based on high performance liquid chromatography (HPLC). C2 is the main paralytic shellfish toxin (PST) detected in a clonal culture of A. tamarense , which is a common causative organism in cases of paralytic shellfish poisoning in Japan. This HPLC method employs post-column fluorescent derivatization (FL). Mobile phase, column size, flow rate, reagent concentrations, and lamp type for the fluorescent detector were all optimized for the detection of C2. With this improved methodology, we could measure 1 fmol of C2 with a signal to noise ratio (S/N) = 2. Clonal heterogeneity within the toxic strain, which was maintained for 13 years after re-isolation from the original clonal culture, ranged from −1 . This report is the first to demonstrate definitively that PST content varies on a cell-by-cell basis in a clonal culture of a dinoflagellate that causes paralytic shellfish poisoning.