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Uwe John - One of the best experts on this subject based on the ideXlab platform.
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Characterization of populations of Alexandrium tamarense by Genotypic and Phenotypic Markers
2020Co-Authors: Tilman J. Alpermann, Urban Tillmann, Uwe John, Allan CembellaAbstract: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.
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SHORT COMMUNICATION Development of specific rRNA probes to distinguish between geographic clades of the Alexandrium tamarense species complex
2020Co-Authors: Uwe John, Linda Medlin, Alfred WegenerAbstract: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.
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a molecular and co evolutionary context for grazer induced toxin production in Alexandrium tamarense
PLOS ONE, 2010Co-Authors: Sylke Wohlrab, Morten Hvitfeldt Iversen, Uwe JohnAbstract: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.
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Six new microsatellite markers for the toxic marine dinoflagellate Alexandrium tamarense
Molecular Ecology Notes, 2006Co-Authors: Tilman J. Alpermann, Uwe John, Linda K. Medlin, Keith J. Edwards, Paul K. Hayes, Katharine M. EvansAbstract: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.
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development of specific rrna probes to distinguish between geographic clades of the Alexandrium tamarense species complex
Journal of Plankton Research, 2004Co-Authors: Uwe John, Linda K. Medlin, R GrobenAbstract: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.
Linda K. Medlin - One of the best experts on this subject based on the ideXlab platform.
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Six new microsatellite markers for the toxic marine dinoflagellate Alexandrium tamarense
Molecular Ecology Notes, 2006Co-Authors: Tilman J. Alpermann, Uwe John, Linda K. Medlin, Keith J. Edwards, Paul K. Hayes, Katharine M. EvansAbstract: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.
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Phylogenetic analysis of selected toxic and non-toxic bacterial strains isolated from the toxic dinoflagellate Alexandrium tamarense
FEMS Microbiology Ecology, 2006Co-Authors: Martina Kopp, Gregory J. Doucette, Masaaki Kodama, Gunnar Gerdts, Christian Schütt, Linda K. MedlinAbstract: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.
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development of specific rrna probes to distinguish between geographic clades of the Alexandrium tamarense species complex
Journal of Plankton Research, 2004Co-Authors: Uwe John, Linda K. Medlin, R GrobenAbstract: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.
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the application of a molecular clock based on molecular sequences and the fossil record to explain biogeographic distributions within the Alexandrium tamarense species complex dinophyceae
Molecular Biology and Evolution, 2003Co-Authors: Uwe John, Robert A Fensome, Linda K. MedlinAbstract:The cosmopolitan dinoflagellate genus Alexandrium, and especially the A. tamarense species complex, contain both toxic and nontoxic strains. An understanding of their evolution and paleogeography is a necessary precursor to unraveling the development and spread of toxic forms. The inclusion of more strains into the existing phylogenetic trees of the Alexandrium tamarense species complex from large subunit rDNA sequences has confirmed that geographic distribution is consistent with the molecular clades but not with the three morphologically defined species that constitute the complex. In addition, a new clade has been discovered, representing Mediterranean nontoxic strains. The dinoflagellates fossil record was used to calibrate a molecular clock: key dates used in this calibration are the origins of the Peridiniales (estimated at 190 MYA), Gonyaulacaceae (180 MYA), and Ceratiaceae (145 MYA). Based on the data set analyzed, the origin of the genus Alexandrium was estimated to be around late Cretaceous (77 MYA), with its earliest possible origination in the mid Cretaceous (119 MYA). The A. tamarense species complex potentially diverged around the early Neogene (23 MYA), with a possible first appearance in the late Paleogene (45 MYA). A paleobiogeographic scenario for Alexandrium is based on (1) the calculated possible ages of origination for the genus and its constituent groups; (2) paleogeographic events determined by plate movements, changing ocean configurations and currents, as well as climatic fluctuations; and (3) the present geographic distribution of the various clades of the Alexandrium tamarense species complex.
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discrimination of the toxigenic dinoflagellates Alexandrium tamarense and a ostenfeldii in co occurring natural populations from scottish coastal waters
European Journal of Phycology, 2003Co-Authors: Uwe John, Allan Cembella, R Groben, C Hummert, Malte Elbrachter, Linda K. MedlinAbstract:Blooms of the toxic dinoflagellate Alexandrium tamarense (Lebour) Balech, a known producer of potent neurotoxins associated with paralytic shellfish poisoning (PSP), are common annual events along the Scottish east coast. The cooccurrence of a second Alexandrium species, A. ostenfeldii (Paulsen) Balech & Tangen is reported in this study from waters of the Scottish east coast. The latter species has been suspected to be an alternative source of PSP toxins in northern Europe. Recent identification of toxic macrocyclic imines known as spirolides in A. ostenfeldii indicates a potential new challenge for monitoring toxic Alexandrium species and their respective toxins in natural populations. In mixed Phytoplankton assemblages, Alexandrium species are difficult to discriminate accurately by conventional light microscopy. Species-specific rRNA probes based upon 18S and 28S ribosomal DNA sequences were developed for A. ostenfeldii and tested by dot-blot and fluorescence in situ hybridization (FISH) techniques. Hy...
Yasukatsu Oshima - One of the best experts on this subject based on the ideXlab platform.
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effect of 5 fluoro 2 deoxyuridine on toxin production and cell cycle regulation in marine dinoflagellate Alexandrium tamarense
Harmful Algae, 2014Co-Authors: Motoo Ogawa, Mari Yotsuyamashita, Yasukatsu OshimaAbstract: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
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Effect of 5-fluoro-2′-deoxyuridine on toxin production and cell cycle regulation in marine dinoflagellate, Alexandrium tamarense
Harmful Algae, 2014Co-Authors: Motoo Ogawa, Mari Yotsu-yamashita, Yasukatsu OshimaAbstract: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
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single cell analysis of paralytic shellfish toxins in Alexandrium tamarense by hplc with post column fluorescent derivatization
Harmful Algae, 2013Co-Authors: Ryoko Ozeki, Mari Yotsuyamashita, Yasukatsu OshimaAbstract: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.
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effects of mitomycin c and colchicine on toxin production and cell cycle regulation in the dinoflagellate Alexandrium tamarense
Harmful Algae, 2011Co-Authors: Motoo Ogawa, Mayumi Hirota, Yasukatsu OshimaAbstract:Abstract Paralytic shellfish toxin (PST) production and cell proliferation in the dinoflagellate Alexandrium tamarense were investigated under the influence of two metabolic inhibitors (mitomycin C and colchicine) that have different mechanisms of action. Intracellular PST levels in cells treated with 2 μM mitomycin C increased gradually, reaching a maximum of 176 fmol/cell (a 6-fold increase). High concentrations of colchicine prolonged G 1 phase in A. tamarense cells, even though colchicine arrests several other eukaryotic cell types in M phase. The cells in prolonged G 1 phase under the influence of colchicine were apparently unable to produce PST. Cell proliferation and toxin production recovered after removal of colchicine; in contrast, the effect of mitomycin C was irreversible. While the timing of toxin production within the cell cycle was not conclusively determined, A. tamarense cells in S phase were able to produce PST.
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toxin composition of resting cysts of Alexandrium tamarense dinophyceae
Toxicon, 1992Co-Authors: Yasukatsu Oshima, Christopher J S Bolch, G M HallegraeffAbstract:Paralytic shellfish toxin composition in the resting cysts of the dinoflagellate Alexandrium tamarense was investigated by means of high performance liquid chromatography. A comparison was made between cysts collected from ship ballast tank sediments, natural population of motile vegetative cells collected from the area where ballast water was taken, as well as cultured vegetative cells established from the cysts and the natural plankton bloom. Total toxin concentration of the cysts (595 fmole/cell) was six-fold higher than that of the natural population of vegetative cells. They contained the same ten toxic components but in different relative abundances. The higher proportion of 11-α-hydroxysulfate epimers in the cysts suggests that the biosynthesis of toxins is halted at an early stage in cyst formation.
R Groben - One of the best experts on this subject based on the ideXlab platform.
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development of specific rrna probes to distinguish between geographic clades of the Alexandrium tamarense species complex
Journal of Plankton Research, 2004Co-Authors: Uwe John, Linda K. Medlin, R GrobenAbstract: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.
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discrimination of the toxigenic dinoflagellates Alexandrium tamarense and a ostenfeldii in co occurring natural populations from scottish coastal waters
European Journal of Phycology, 2003Co-Authors: Uwe John, Allan Cembella, R Groben, C Hummert, Malte Elbrachter, Linda K. MedlinAbstract:Blooms of the toxic dinoflagellate Alexandrium tamarense (Lebour) Balech, a known producer of potent neurotoxins associated with paralytic shellfish poisoning (PSP), are common annual events along the Scottish east coast. The cooccurrence of a second Alexandrium species, A. ostenfeldii (Paulsen) Balech & Tangen is reported in this study from waters of the Scottish east coast. The latter species has been suspected to be an alternative source of PSP toxins in northern Europe. Recent identification of toxic macrocyclic imines known as spirolides in A. ostenfeldii indicates a potential new challenge for monitoring toxic Alexandrium species and their respective toxins in natural populations. In mixed Phytoplankton assemblages, Alexandrium species are difficult to discriminate accurately by conventional light microscopy. Species-specific rRNA probes based upon 18S and 28S ribosomal DNA sequences were developed for A. ostenfeldii and tested by dot-blot and fluorescence in situ hybridization (FISH) techniques. Hy...
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16s rrna targeted probes for the identification of bacterial strains isolated from cultures of the toxic dinoflagellate Alexandrium tamarense
Microbial Ecology, 2000Co-Authors: R Groben, Gregory J. Doucette, Masaaki Kodama, Marie R G Kopp, Rudolf Amann, Linda K. MedlinAbstract:: A BSTRACTBacteria have been implicated in the production of paralytic shellfish poison (PSP) toxins, which are normally associated with bloom-forming algal species, specifically toxic dinoflagellate algae. To clarify the role that these bacteria may play in the production of PSP toxins, it is desirable to identify and localize the bacteria associated with the dinoflagellates. 16S rRNA-targeted probes offer the possibility for both, and thus, probes have been made to putatively toxigenic bacteria isolated from the PSP-related dinoflagellate Alexandrium tamarense and tested for their specificity in dot blot and in situ hybridization experiments.
Carmelo R Tomas - One of the best experts on this subject based on the ideXlab platform.
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recurrent vernal presence of the toxic Alexandrium tamarense Alexandrium fundyense dinoflagellata species complex in narragansett bay usa
Harmful Algae, 2014Co-Authors: David G Borkman, Theodore J Smayda, Erika N Schwarz, Leanne J Flewelling, Carmelo R TomasAbstract:Abstract The vernal occurrence of toxic dinoflagellates in the Alexandrium tamarense/Alexandrium fundyense species complex in an enclosed embayment of Narragansett Bay (Wickford Cove, Rhode Island) was documented during 2005 and 2009–2012. This is the first report of regular appearance of the Alexandrium fundyense/Alexandrium tamarense species complex in Narragansett Bay. Thecal plate analysis of clonal isolates using SEM revealed cells morphologically consistent with both Alexandrium tamarense Lebour (Balech) and Alexandrium fundyense Balech. Additionally, molecular analyses confirmed that the partial sequences for 18S through the D1–D2 region of 28S were consistent with the identity of the two Alexandrium species. Toxin analyses revealed the presence of a suite of toxins (C1/2, B1 (GTX-5), STX, GTX-2/3. Neo, and GTX-1/4) in both Alexandrium tamarense (6.31 fmol cell −1 STX equiv.) and Alexandrium fundyense (9.56 fmol cell −1 STX equiv.) isolated from Wickford Cove; the toxicity of a Narragansett Bay Alexandrium peruvianum isolate (1.79 fmol cell −1 STX equiv.) was also determined. Combined Alexandrium tamarense / Alexandrium fundyense abundance in Wickford Cove reached a peak abundance of 1280 cells L −1 (May of 2010), with the combined abundance routinely exceeding levels leading to shellfishing closures in other systems. The toxic Alexandrium tamarense / Alexandrium fundyense species complex appears to be a regular component of the lower Narragansett Bay phytoplankton community, either newly emergent or previously overlooked by extant monitoring programs.
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Recurrent vernal presence of the toxic Alexandrium tamarense/Alexandrium fundyense (Dinoflagellata) species complex in Narragansett Bay, USA
Harmful Algae, 2014Co-Authors: David G Borkman, Theodore J Smayda, Erika N Schwarz, Leanne J Flewelling, Carmelo R TomasAbstract:Abstract The vernal occurrence of toxic dinoflagellates in the Alexandrium tamarense/Alexandrium fundyense species complex in an enclosed embayment of Narragansett Bay (Wickford Cove, Rhode Island) was documented during 2005 and 2009–2012. This is the first report of regular appearance of the Alexandrium fundyense/Alexandrium tamarense species complex in Narragansett Bay. Thecal plate analysis of clonal isolates using SEM revealed cells morphologically consistent with both Alexandrium tamarense Lebour (Balech) and Alexandrium fundyense Balech. Additionally, molecular analyses confirmed that the partial sequences for 18S through the D1–D2 region of 28S were consistent with the identity of the two Alexandrium species. Toxin analyses revealed the presence of a suite of toxins (C1/2, B1 (GTX-5), STX, GTX-2/3. Neo, and GTX-1/4) in both Alexandrium tamarense (6.31 fmol cell −1 STX equiv.) and Alexandrium fundyense (9.56 fmol cell −1 STX equiv.) isolated from Wickford Cove; the toxicity of a Narragansett Bay Alexandrium peruvianum isolate (1.79 fmol cell −1 STX equiv.) was also determined. Combined Alexandrium tamarense / Alexandrium fundyense abundance in Wickford Cove reached a peak abundance of 1280 cells L −1 (May of 2010), with the combined abundance routinely exceeding levels leading to shellfishing closures in other systems. The toxic Alexandrium tamarense / Alexandrium fundyense species complex appears to be a regular component of the lower Narragansett Bay phytoplankton community, either newly emergent or previously overlooked by extant monitoring programs.
