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Uwe John - One of the best experts on this subject based on the ideXlab platform.
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gene duplication loss and selection in the evolution of saxitoxin biosynthesis in alveolates
Molecular Phylogenetics and Evolution, 2015Co-Authors: Shauna A Murray, Rutuja Diwan, Russell J S Orr, Gurjeet S Kohli, Uwe JohnAbstract:A group of marine dinoflagellates (Alveolata, Eukaryota), consisting of ∼10 species of the genus Alexandrium, Gymnodinium catenatum and Pyrodinium bahamense, produce the toxin saxitoxin and its analogues (STX), which can accumulate in shellfish, leading to ecosystem and human health impacts. The genes, sxt, putatively involved in STX biosynthesis, have recently been identified, however, the evolution of these genes within dinoflagellates is not clear. There are two reasons for this: uncertainty over the phylogeny of dinoflagellates; and that the sxt genes of many species of Alexandrium and other dinoflagellate genera are not known. Here, we determined the phylogeny of STX-producing and other dinoflagellates based on a concatenated eight-gene alignment. We determined the presence, diversity and phylogeny of sxtA, domains A1 and A4 and sxtG in 52 strains of Alexandrium, and a further 43 species of dinoflagellates and thirteen other alveolates. We confirmed the presence and high sequence conservation of sxtA, domain A4, in 40 strains (35 Alexandrium, 1 Pyrodinium, 4 Gymnodinium) of 8 species of STX-producing dinoflagellates, and absence from non-producing species. We found three paralogs of sxtA, domain A1, and a widespread distribution of sxtA1 in non-STX producing dinoflagellates, indicating duplication events in the evolution of this gene. One paralog, clade 2, of sxtA1 may be particularly related to STX biosynthesis. Similarly, sxtG appears to be generally restricted to STX-producing species, while three amidinotransferase gene paralogs were found in dinoflagellates. We investigated the role of positive (diversifying) selection following duplication in sxtA1 and sxtG, and found negative selection in clades of sxtG and sxtA1, clade 2, suggesting they were functionally constrained. Significant episodic diversifying selection was found in some strains in clade 3 of sxtA1, a clade that may not be involved in STX biosynthesis, indicating pressure for diversification of function.
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intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population
Proceedings of The Royal Society B: Biological Sciences, 2015Co-Authors: Uwe John, Tilman J. Alpermann, Urban Tillmann, Sylke Wohlrab, Jennifer Hulskotter, Dedmer B Van De WaalAbstract:Dinoflagellates are a major cause of harmful algal blooms (HABs), with consequences for coastal marine ecosystem functioning and services. Alexandrium fundyense (previously Alexandrium tamarense) is one of the most abundant and widespread toxigenic species in the temperate Northern and Southern Hemisphere and produces paralytic shellfish poisoning toxins as well as lytic allelochemical substances. These bioactive compounds may support the success of A. fundyense and its ability to form blooms. Here we investigate the impact of grazing on monoclonal and mixed set-ups of highly (Alex2) and moderately (Alex4) allelochemically active A. fundyense strains and a non-allelochemically active conspecific (Alex5) by the heterotrophic dinoflagellate Polykrikos kofoidii. While Alex4 and particularly Alex5 were strongly grazed by P. kofoidii when offered alone, both strains grew well in the mixed assemblages (Alex4 + Alex5 and Alex2 + Alex5). Hence, the allelochemical active strains facilitated growth of the non-active strain by protecting the population as a whole against grazing. Based on our results, we argue that facilitation among clonal lineages within a species may partly explain the high genotypic and phenotypic diversity of Alexandrium populations. Populations of Alexandrium may comprise multiple cooperative traits that act in concert with intraspecific facilitation, and hence promote the success of this notorious HAB species.
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comparative genomic and transcriptomic characterization of the toxigenic marine dinoflagellate Alexandrium ostenfeldii
PLOS ONE, 2011Co-Authors: Nina Jaeckisch, Ines Yang, Sylke Wohlrab, Juergen Kroymann, Allan Cembella, Heiko Vogel, Gernot Glöckner, Uwe JohnAbstract:Many dinoflagellate species are notorious for the toxins they produce and ecological and human health consequences associated with harmful algal blooms (HABs). Dinoflagellates are particularly refractory to genomic analysis due to the enormous genome size, lack of knowledge about their DNA composition and structure, and peculiarities of gene regulation, such as spliced leader (SL) trans-splicing and mRNA transposition mechanisms. Alexandrium ostenfeldii is known to produce macrocyclic imine toxins, described as spirolides. We characterized the genome of A. ostenfeldii using a combination of transcriptomic data and random genomic clones for comparison with other dinoflagellates, particularly Alexandrium species. Examination of SL sequences revealed similar features as in other dinoflagellates, including Alexandrium species. SL sequences in decay indicate frequent retro-transposition of mRNA species. This probably contributes to overall genome complexity by generating additional gene copies. Sequencing of several thousand fosmid and bacterial artificial chromosome (BAC) ends yielded a wealth of simple repeats and tandemly repeated longer sequence stretches which we estimated to comprise more than half of the whole genome. Surprisingly, the repeats comprise a very limited set of 79–97 bp sequences; in part the genome is thus a relatively uniform sequence space interrupted by coding sequences. Our genomic sequence survey (GSS) represents the largest genomic data set of a dinoflagellate to date. Alexandrium ostenfeldii is a typical dinoflagellate with respect to its transcriptome and mRNA transposition but demonstrates Alexandrium-like stop codon usage. The large portion of repetitive sequences and the organization within the genome is in agreement with several other studies on dinoflagellates using different approaches. It remains to be determined whether this unusual composition is directly correlated to the exceptionally genome organization of dinoflagellates with a low amount of histones and histone-like proteins.
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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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allelochemical interactions and short term effects of the dinoflagellate Alexandrium on selected photoautotrophic and heterotrophic protists
Harmful Algae, 2008Co-Authors: Urban Tillmann, Tilman J. Alpermann, Uwe John, Allan CembellaAbstract:The marine dinoflagellate genus Alexandrium (Halim) Balech contains members that produce highly potent phycotoxins (PSP toxins or spirolides) as well as lytic substances and other allelochemicals of unknown structure and ecological significance. One isolate each of six Alexandrium species (A. tamarense, A. ostenfeldii, A. lusitanicum, A. minutum, A. catenella, A. taylori), of the closely related gonyaulacoid dinoflagellate Fragilidium subglobosum, and of the peridinioid Scrippsiella trochoidea were tested in 24 h co-incubation experiments for their short-term deleterious effects on a diversity of marine protists. Both autotrophs (Rhodomonas salina, Dunaliella salina, Thalassiosira weissflogii) and heterotrophs (Oxyrrhis marina, Amphidinium crassum, Rimostrombidium caudatum) were included as target species. All donor isolates except S. trochoidea exhibited lytic effects on at least some target species. Lytic effects were observed with all Alexandrium species, for both whole cell samples and culture filtrate (<10 μm and <0.2 μm). Antibiotic treated cultures with drastically reduced bacterial numbers did not show any general reduction in lytic capacity, therefore direct involvement of extracellular bacteria in allelochemical production is unlikely. Values of EC50, defined as the Alexandrium cell concentration causing lysis of 50% of target cells, differed by two orders of magnitude depending on the donor/target combination, from 3.1 × 103 cells ml−1 (A. minutum/O. marina) down to 0.02 × 103 cells ml−1 (A. catenella/D. salina). Within the array of nine donor Alexandrium/target combinations, variable ratios in EC50 values between donor/target combination cannot be explained by quantitative differences in allelochemical production, but rather indicate qualitative differences in the composition of compounds produced by different Alexandrium strains. In conclusion, our study confirms the widespread lytic capacity within the genus Alexandrium, although allelochemical effects are not restricted to this genus. Allelochemical interactions mediated by such lytic substances may be significant in explaining the formation and maintenance of Alexandrium blooms through direct destructive effects on competing algae or unicellular grazers.
Donald M Anderson - One of the best experts on this subject based on the ideXlab platform.
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effects of temperature and salinity on the growth of Alexandrium dinophyceae isolates from the salish sea
Journal of Phycology, 2016Co-Authors: Brian D Bill, Donald M Anderson, Stephanie K Moore, Levi R Hay, Vera L TrainerAbstract:Toxin-producing blooms of dinoflagellates in the genus Alexandrium have plagued the inhabitants of the Salish Sea for centuries. Yet the environmental conditions that promote accelerated growth of this organism, a producer of paralytic shellfish toxins, is lacking. This study quantitatively determined the growth response of two Alexandrium isolates to a range of temperatures and salinities, factors that will strongly respond to future climate change scenarios. An empirical equation, derived from observed growth rates describing the temperature and salinity dependence of growth, was used to hindcast bloom risk. Hindcasting was achieved by comparing predicted growth rates, calculated from in situ temperature and salinity data from Quartermaster Harbor, with corresponding Alexandrium cell counts and shellfish toxin data. The greatest bloom risk, defined at μ >0.25 d(-1) , generally occurred from April through November annually; however, growth rates rarely fell below 0.10 d(-1) . Except for a few occasions, Alexandrium cells were only observed during the periods of highest bloom risk and paralytic shellfish toxins above the regulatory limit always fell within the periods of predicted bloom occurrence. While acknowledging that Alexandrium growth rates are affected by other abiotic and biotic factors, such as grazing pressure and nutrient availability, the use of this empirical growth function to predict higher risk time frames for blooms and toxic shellfish within the Salish Sea provides the groundwork for a more comprehensive biological model of Alexandrium bloom dynamics in the region and will enhance our ability to forecast blooms in the Salish Sea under future climate change scenarios.
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the effects of elevated co2 on the growth and toxicity of field populations and cultures of the saxitoxin producing dinoflagellate Alexandrium fundyense
Limnology and Oceanography, 2015Co-Authors: Theresa K Hattenrathlehmann, Donald M Anderson, Juliette L Smith, Ryan B Wallace, Lucas R Merlo, Florian Koch, Heidi Mittelsdorf, Jennifer A Goleski, Christopher J. GoblerAbstract:The effects of coastal acidification on the growth and toxicity of the saxitoxin-producing dinoflagellate Alexandrium fundyense were examined in culture and ecosystem studies. In culture experiments, Alexandrium strains isolated from Northport Bay, New York, and the Bay of Fundy, Canada, grew significantly faster (16–190%; p < 0.05) when exposed to elevated levels of PCO2 (∼ 90–190 Pa = 900–1900 μatm) compared to lower levels (∼ 40 Pa = 400 μatm). Exposure to higher levels of PCO2 also resulted in significant increases (71–81%) in total cellular toxicity (fg saxitoxin equivalents cell−1) in the Northport Bay strain, while no changes in toxicity were detected in the Bay of Fundy strain. The positive relationship between PCO2 enrichment and elevated growth was reproducible in natural populations from New York waters. Alexandrium densities were significantly and consistently enhanced when natural populations were incubated at 150 Pa PCO2 compared to ∼ 39 Pa. During natural Alexandrium blooms in Northport Bay, PCO2 concentrations increased over the course of a bloom to more than 170 Pa and were highest in regions with the greatest Alexandrium abundances, suggesting Alexandrium may further exacerbate acidification and/or be especially adapted to these acidified conditions. The co-occurrence of Alexandrium blooms and elevated PCO2 represents a previously unrecognized, compounding environmental threat to coastal ecosystems. The ability of elevated PCO2 to enhance the growth and toxicity of Alexandrium indicates that acidification promoted by eutrophication or climate change can intensify these, and perhaps other, harmful algal blooms.
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the globally distributed genus Alexandrium multifaceted roles in marine ecosystems and impacts on human health
Harmful Algae, 2012Co-Authors: Donald M Anderson, Tilman J. Alpermann, Allan Cembella, Yves Collos, Estelle Masseret, Marina MontresorAbstract:The dinoflagellate genus Alexandrium is one of the major harmful algal bloom (HAB) genera with respect to the diversity, magnitude and consequences of blooms. The ability of Alexandrium to colonize multiple habitats and to persist over large regions through time is testimony to the adaptability and resilience of this group of species. Three different families of toxins, as well as an as yet incompletely characterized suite of allelochemicals are produced among Alexandrium species. Nutritional strategies are equally diverse, including the ability to utilize a range of inorganic and organic nutrient sources, and feeding by ingestion of other organisms. Many Alexandrium species have complex life histories that include sexuality and often, but not always, cyst formation, which is characteristic of a meroplanktonic life strategy and offers considerable ecological advantages. Due to the public health and ecosystem impacts of Alexandrium blooms, the genus has been extensively studied, and there exists a broad knowledge base that ranges from taxonomy and phylogeny through genomics and toxin biosynthesis to bloom dynamics and modeling. Here we present a review of the genus Alexandrium, focusing on the major toxic and otherwise harmful species.
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intercalibration of classical and molecular techniques for identification of Alexandrium fundyense dinophyceae and estimation of cell densities
Harmful Algae, 2007Co-Authors: Anna Godhe, Eileen Bresnan, Allan Cembella, Caroline Cusack, John Pedersen, Per Kragh Andersen, Donald M Anderson, Einar Dahl, Sonja Diercks, Malte ElbrachterAbstract:A workshop with the aim to compare classical and molecular techniques for phytoplankton enumeration took place at Kristineberg Marine Research Station, Sweden, in August 2005. Seventeen different techniques ‐ nine classical microscopic-based and eight molecular methods ‐ were compared. Alexandrium fundyense was the target organism in four experiments. Experiment 1 was designed to determine the range of cell densities over which the methods were applicable. Experiment 2 tested the species specificity of the methods by adding Alexandrium ostenfeldii, to samples containing A. fundyense. Experiments 3 and 4 tested the ability of the methods to detect the target organism within a natural phytoplankton community. Most of the methods could detect
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molecular evolution of the Alexandrium tamarense species complex dinophyceae dispersal in the north american and west pacific regions
Phycologia, 1995Co-Authors: Christopher A Scholin, G M Hallegraeff, Donald M AndersonAbstract:Hypotheses concerning the molecular evolution, population structure and dispersal of the toxic dinoflagellates Alexandrium tamarense (Lebour) Balech, A. catenella (Whedon et Kofoid) Balech and A. f...
Lei Shi - One of the best experts on this subject based on the ideXlab platform.
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loop mediated isothermal amplification method for rapid detection of the toxic dinoflagellate Alexandrium which causes algal blooms and poisoning of shellfish
Fems Microbiology Letters, 2008Co-Authors: Li Wang, Muhammad Jahangir Alam, Yuhuan Geng, Shinji Yamasaki, Lei ShiAbstract:The marine dinoflagellate genus Alexandrium includes a number of species that produce potent neurotoxins responsible for paralytic shellfish poisoning, which in humans may cause muscular paralysis, neurological symptoms and, in extreme cases, death. Because of the genetic diversity of different genera and species, molecular tools may help to detect the presence of target microorganisms in marine field samples. Here we employed a loop-mediated isothermal amplification (LAMP) method for the rapid and simple detection of toxic Alexandrium species. A set of four primers were designed based upon the conserved region of the 5.8S rRNA gene of members of the genus Alexandrium. Using this detection system, toxic Alexandrium genes were amplified and visualized as a ladder-like pattern of bands on agarose gels under isothermal condition within 60 min. The LAMP amplicons were also directly visualized by eye in the reaction tube by the addition of SYBR Green I. This LAMP assay was 10-fold more sensitive than a conventional PCR method with a detection limit of 5 cells per tube when targeting DNA from Alexandrium minutum. The LAMP assay reported here indicates the potential usefulness of the technique as a valuable simple, rapid alternative procedure for the detection of target toxic Alexandrium species during coastal water monitoring.
Allan Cembella - One of the best experts on this subject based on the ideXlab platform.
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the globally distributed genus Alexandrium multifaceted roles in marine ecosystems and impacts on human health
Harmful Algae, 2012Co-Authors: Donald M Anderson, Tilman J. Alpermann, Allan Cembella, Yves Collos, Estelle Masseret, Marina MontresorAbstract:The dinoflagellate genus Alexandrium is one of the major harmful algal bloom (HAB) genera with respect to the diversity, magnitude and consequences of blooms. The ability of Alexandrium to colonize multiple habitats and to persist over large regions through time is testimony to the adaptability and resilience of this group of species. Three different families of toxins, as well as an as yet incompletely characterized suite of allelochemicals are produced among Alexandrium species. Nutritional strategies are equally diverse, including the ability to utilize a range of inorganic and organic nutrient sources, and feeding by ingestion of other organisms. Many Alexandrium species have complex life histories that include sexuality and often, but not always, cyst formation, which is characteristic of a meroplanktonic life strategy and offers considerable ecological advantages. Due to the public health and ecosystem impacts of Alexandrium blooms, the genus has been extensively studied, and there exists a broad knowledge base that ranges from taxonomy and phylogeny through genomics and toxin biosynthesis to bloom dynamics and modeling. Here we present a review of the genus Alexandrium, focusing on the major toxic and otherwise harmful species.
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comparative genomic and transcriptomic characterization of the toxigenic marine dinoflagellate Alexandrium ostenfeldii
PLOS ONE, 2011Co-Authors: Nina Jaeckisch, Ines Yang, Sylke Wohlrab, Juergen Kroymann, Allan Cembella, Heiko Vogel, Gernot Glöckner, Uwe JohnAbstract:Many dinoflagellate species are notorious for the toxins they produce and ecological and human health consequences associated with harmful algal blooms (HABs). Dinoflagellates are particularly refractory to genomic analysis due to the enormous genome size, lack of knowledge about their DNA composition and structure, and peculiarities of gene regulation, such as spliced leader (SL) trans-splicing and mRNA transposition mechanisms. Alexandrium ostenfeldii is known to produce macrocyclic imine toxins, described as spirolides. We characterized the genome of A. ostenfeldii using a combination of transcriptomic data and random genomic clones for comparison with other dinoflagellates, particularly Alexandrium species. Examination of SL sequences revealed similar features as in other dinoflagellates, including Alexandrium species. SL sequences in decay indicate frequent retro-transposition of mRNA species. This probably contributes to overall genome complexity by generating additional gene copies. Sequencing of several thousand fosmid and bacterial artificial chromosome (BAC) ends yielded a wealth of simple repeats and tandemly repeated longer sequence stretches which we estimated to comprise more than half of the whole genome. Surprisingly, the repeats comprise a very limited set of 79–97 bp sequences; in part the genome is thus a relatively uniform sequence space interrupted by coding sequences. Our genomic sequence survey (GSS) represents the largest genomic data set of a dinoflagellate to date. Alexandrium ostenfeldii is a typical dinoflagellate with respect to its transcriptome and mRNA transposition but demonstrates Alexandrium-like stop codon usage. The large portion of repetitive sequences and the organization within the genome is in agreement with several other studies on dinoflagellates using different approaches. It remains to be determined whether this unusual composition is directly correlated to the exceptionally genome organization of dinoflagellates with a low amount of histones and histone-like proteins.
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allelochemical interactions and short term effects of the dinoflagellate Alexandrium on selected photoautotrophic and heterotrophic protists
Harmful Algae, 2008Co-Authors: Urban Tillmann, Tilman J. Alpermann, Uwe John, Allan CembellaAbstract:The marine dinoflagellate genus Alexandrium (Halim) Balech contains members that produce highly potent phycotoxins (PSP toxins or spirolides) as well as lytic substances and other allelochemicals of unknown structure and ecological significance. One isolate each of six Alexandrium species (A. tamarense, A. ostenfeldii, A. lusitanicum, A. minutum, A. catenella, A. taylori), of the closely related gonyaulacoid dinoflagellate Fragilidium subglobosum, and of the peridinioid Scrippsiella trochoidea were tested in 24 h co-incubation experiments for their short-term deleterious effects on a diversity of marine protists. Both autotrophs (Rhodomonas salina, Dunaliella salina, Thalassiosira weissflogii) and heterotrophs (Oxyrrhis marina, Amphidinium crassum, Rimostrombidium caudatum) were included as target species. All donor isolates except S. trochoidea exhibited lytic effects on at least some target species. Lytic effects were observed with all Alexandrium species, for both whole cell samples and culture filtrate (<10 μm and <0.2 μm). Antibiotic treated cultures with drastically reduced bacterial numbers did not show any general reduction in lytic capacity, therefore direct involvement of extracellular bacteria in allelochemical production is unlikely. Values of EC50, defined as the Alexandrium cell concentration causing lysis of 50% of target cells, differed by two orders of magnitude depending on the donor/target combination, from 3.1 × 103 cells ml−1 (A. minutum/O. marina) down to 0.02 × 103 cells ml−1 (A. catenella/D. salina). Within the array of nine donor Alexandrium/target combinations, variable ratios in EC50 values between donor/target combination cannot be explained by quantitative differences in allelochemical production, but rather indicate qualitative differences in the composition of compounds produced by different Alexandrium strains. In conclusion, our study confirms the widespread lytic capacity within the genus Alexandrium, although allelochemical effects are not restricted to this genus. Allelochemical interactions mediated by such lytic substances may be significant in explaining the formation and maintenance of Alexandrium blooms through direct destructive effects on competing algae or unicellular grazers.
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intercalibration of classical and molecular techniques for identification of Alexandrium fundyense dinophyceae and estimation of cell densities
Harmful Algae, 2007Co-Authors: Anna Godhe, Eileen Bresnan, Allan Cembella, Caroline Cusack, John Pedersen, Per Kragh Andersen, Donald M Anderson, Einar Dahl, Sonja Diercks, Malte ElbrachterAbstract:A workshop with the aim to compare classical and molecular techniques for phytoplankton enumeration took place at Kristineberg Marine Research Station, Sweden, in August 2005. Seventeen different techniques ‐ nine classical microscopic-based and eight molecular methods ‐ were compared. Alexandrium fundyense was the target organism in four experiments. Experiment 1 was designed to determine the range of cell densities over which the methods were applicable. Experiment 2 tested the species specificity of the methods by adding Alexandrium ostenfeldii, to samples containing A. fundyense. Experiments 3 and 4 tested the ability of the methods to detect the target organism within a natural phytoplankton community. Most of the methods could detect
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zooplankton grazing impacts on Alexandrium spp in the nearshore environment of the gulf of maine
Deep-sea Research Part Ii-topical Studies in Oceanography, 2005Co-Authors: Robert G. Campbell, Gregory J Teegarden, Allan Cembella, Edward G. DurbinAbstract:Abstract We collected samples at weekly intervals from several stations in coastal waters of the Gulf of Maine during the spring of 1998 and 1999 for zooplankton and phytoplankton abundance, biomass, species composition, and toxin content. In addition, grazing rates of zooplankton were determined using natural water from selected stations. During 1998, there was a moderate bloom of the paralytic shellfish poison (PSP) producing dinoflagellates Alexandrium spp. (3000 cells/L), while in 1999 concentrations were very low throughout the study. In 1998, potential zooplankton grazing-impacts on Alexandrium spp. increased from 0 to 0.8 day −1 in concert with the vernal increase in zooplankton biomass and appeared to contribute to the bloom's demise. During the 1998 bloom, PSP toxin levels in zooplankton tissues appeared to be sufficient to pose risks to higher trophic levels, such as fishes and marine mammals. Our findings suggest that zooplankton grazing can be an important source of mortality for harmful algal bloom species such as Alexandrium spp.
Mariângela Menezes - One of the best experts on this subject based on the ideXlab platform.
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morphology and molecular phylogeny of a new pst producing dinoflagellate species Alexandrium fragae sp nov gonyaulacales dinophyceae
Harmful Algae, 2020Co-Authors: Suema Branco, Fabiano Salgueiro, Mair M M Oliveira, Mauro C P Vilar, Sandra M F O Azevedo, Mariângela MenezesAbstract:The genus Alexandrium comprises some of the most potentially toxic marine algae. A new toxic species of Alexandrium, A. fragae sp. nov., was found in Guanabara Bay, Rio de Janeiro, southern Brazil. The new species produces GTX2&3 and STX. The cell morphology of A. fragae resembles A. minutum in many characters, including the small size; the rounded-elliptical shape; and the shapes of the apical pore complex (APC), first apical plate (1'), sixth precingular plate (6″), and anterior and posterior sulcal plates (s.a. and s.p.). The main diagnostic characters of A. fragae are the ornamentation pattern, smooth epitheca and reticulated hypotheca, all of which were present in both natural populations and cultures. Phylogenies inferred from the ITS, LSU, and SSU rDNA of A. fragae showed that A. fragae clustered in a well-supported clade, distinct from other Alexandrium species. Morphology and molecular analyses based on ITS and LSU rDNA indicated that A. fragae strains and Alexandrium sp. from Japan (D163C5, D164C6) are a single species. Our findings suggest that the Alexandrium morphotype with a smooth epitheca and reticulated hypotheca, previously identified as A. minutum in different geographic regions, may corresponds to A. fragae.
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Table_1_The Genus Alexandrium (Dinophyceae, Dinophyta) in Brazilian Coastal Waters.docx
2018Co-Authors: Mariângela Menezes, Suema Branco, Maria Cecília Miotto, Catharina Alves-de-souzaAbstract:A review of the dinoflagellate genus Alexandrium occurring in Brazilian coastal waters is presented based on both published information and new data. Seven Alexandrium species have been recorded from Brazil so far: Alexandrium catenella, Alexandrium fraterculus, Alexandrium gaardnerae, Alexandrium kutnerae, Alexandrium tamiyavanichi, Alexandrium tamutum, and Alexandrium sp. While A. gaardnerae and A. kutnerae were identified based only on morphological characteristics, phylogenetic analysis (ITS and LSU rDNA) were performed for the remaining species based on cultures and/or field populations. Monoclonal cultures of the analyzed species were isolated from field samples obtained from Bahia (A. tamiyavanichi, two strains), Rio de Janeiro (A. tamutum, three strains; Alexandrium sp., two strains), Santa Catarina (A. fraterculus, one strain), and Rio Grande do Sul (Alexandrium tamarense, three strains). This is the first record of A. tamutum for the South Atlantic. In addition, molecular data for Brazilian strains of A. fraterculus are presented for the first time, as well as sequences from the ITS region for A. catenella (previously reported as A. tamarense) from Brazilian coastal waters. The morphological characters of the three species corresponded to those typically recorded in the literature and their identification was confirmed by molecular analysis. Based on the LSU rDNA and ITS regions, the three strains of A. catenella showed a high degree of similarity with strains from Southern Chile and North America. The implications and limitations of these findings for the monitoring protocols within the global and regional context are discussed.
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The Genus Alexandrium (Dinophyceae, Dinophyta) in Brazilian Coastal Waters
Frontiers Media S.A., 2018Co-Authors: Mariângela Menezes, Suema Branco, Maria Cecília Miotto, Catharina Alves-de-souzaAbstract:A review of the dinoflagellate genus Alexandrium occurring in Brazilian coastal waters is presented based on both published information and new data. Seven Alexandrium species have been recorded from Brazil so far: Alexandrium catenella, Alexandrium fraterculus, Alexandrium gaardnerae, Alexandrium kutnerae, Alexandrium tamiyavanichi, Alexandrium tamutum, and Alexandrium sp. While A. gaardnerae and A. kutnerae were identified based only on morphological characteristics, phylogenetic analysis (ITS and LSU rDNA) were performed for the remaining species based on cultures and/or field populations. Monoclonal cultures of the analyzed species were isolated from field samples obtained from Bahia (A. tamiyavanichi, two strains), Rio de Janeiro (A. tamutum, three strains; Alexandrium sp., two strains), Santa Catarina (A. fraterculus, one strain), and Rio Grande do Sul (Alexandrium tamarense, three strains). This is the first record of A. tamutum for the South Atlantic. In addition, molecular data for Brazilian strains of A. fraterculus are presented for the first time, as well as sequences from the ITS region for A. catenella (previously reported as A. tamarense) from Brazilian coastal waters. The morphological characters of the three species corresponded to those typically recorded in the literature and their identification was confirmed by molecular analysis. Based on the LSU rDNA and ITS regions, the three strains of A. catenella showed a high degree of similarity with strains from Southern Chile and North America. The implications and limitations of these findings for the monitoring protocols within the global and regional context are discussed
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identification of the toxic alga Alexandrium tamiyavanichi dinophyceae from northeastern brazil a combined morphological and rdna sequence partial lsu and its approach1
Journal of Phycology, 2010Co-Authors: Mariângela Menezes, Daniel Varela, Luis Antonio De Oliveira Proenca, Marcio Da Silva Tamanaha, Javier ParedesAbstract:Morphological and phylogenetic analyses and sequencing of the partial LSU gene and internal transcribed spacer (ITS) regions of the rDNA gene were combined to study toxic strains of Alexandrium tamiyavanichi Balech collected from northeastern Brazilian coastal waters. All specimens were identified with A. tamiyavanichi mainly based on the shape of the anterior sulcal plate (S.a.), which was the most conservative character. Among the specimens studied, 8% did not conform to the morphological description of A. tamiyavanichi. The occurrence of transitory states between A. tamiyavanichi and Alexandrium cohorticula (Balech) Balech tended to confirm that both species are conspecific. The posterior sulcal plate (S.p.) was not a good taxonomic character as variability in its shape did not allow a clear assignment of specimens from the same clonal isolate to either morphologically defined species. Phylogenetic analyses confirmed the overall validity of morphological characters to delineate the evolutionary relationships among the clades of Alexandrium species analyzed here, indicating that A. tamiyavanchi is a valid species according to the morphological species concept. This analysis showed that the Brazilian strains form a monophyletic clade with Asiatic strains of A. tamiyavanichi, but with enough genetic distance to argue for long-term separation and isolation of locally established populations, extending the known biogeographic range of this species. On the higher phylogenetic level, our data also indicate that Alexandrium tropicale Balech forms part of the clade otherwise consisting of the morphologically defined freterculus group, and this A. tamiyavanichi/tropicale/fraterculus (Balech) Balech clade (including species from the formerly termed tropical Asian [TROP] clade) may be considered as a sister group of the Alexandrium tamarense species complex.