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  • 1
    Electronic Resource
    Electronic Resource
    Phylogenetic and functional diversity of the cultivable bacterial community associated with the paralytic shellfish poisoning dinoflagellate Gymnodinium catenatum (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 47 (2004), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Gymnodinium catenatum is one of several dinoflagellates that produce a suite of neurotoxins called the paralytic shellfish toxins (PST), responsible for outbreaks of paralytic shellfish poisoning in temperate and tropical waters. Previous research suggested that the bacteria associated with the surface of the sexual resting stages (cyst) were important to the production of PST by G. catenatum. This study sought to characterise the cultivable bacterial diversity of seven different strains of G. catenatum that produce both high and abnormally low amounts of PST, with the long-term aim of understanding the role the bacterial flora has in bloom development and toxicity of this alga. Sixty-one bacterial isolates were cultured and phylogenetically identified as belonging to the Proteobacteria (70%), Bacteroidetes (26%) or Actinobacteria (3%). The Alphaproteobacteria were the most numerous both in terms of the number of isolates cultured (49%) and were also the most abundant type of bacteria in each G. catenatum culture. Two phenotypic (functional) traits inferred from the phylogenetic data were shown to be a common feature of the bacteria present in each G. catenatum culture: firstly, Alphaproteobacteria capable of aerobic anoxygenic photosynthesis, and secondly, Gammaproteobacteria capable of hydrocarbon utilisation and oligotrophic growth. In relation to reports of autonomous production of PST by dinoflagellate-associated bacteria, PST production by bacterial isolates was investigated, but none were shown to produce any PST-like toxins. Overall, this study has identified a number of emergent trends in the bacterial community of G. catenatum which are mirrored in the bacterial flora of other dinoflagellates, and that are likely to be of especial relevance to the population dynamics of natural and harmful algal blooms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0168-6496(03)00298-8
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Isolation and purification of Australian isolates of the toxic cyanobacteriumMicrocystis aeruginosa Kütz (1996)
    Springer
    Journal of applied phycology 8 (1996), S. 5-13 
    Details
    ISSN: 1573-5176
    Keywords: axenic culture ; cyanobacteria ; Microcystis ; toxic ; Spirochaeta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolation and laboratory culture ofMicrocystis aeruginosa Kütz. using a growth medium (MLA medium) suitable for both non-axenic and axenic cultures is described. Seventeen established strains ofM. aeruginosa were subjected to one or more of three purification methods: centrifugation cleaning, sulphide gradient selection, and antibiotic treatment (Imipenem®). While each method purified only about half of the strains attempted, the selective application of each method, based on the morphological characteristics of the strains, succeeded in purifying 12 of the 17 strains. Three of the 5 strains not purified were contaminated with a sulphide-tolerant, Imipenem-resistant spirochaete,Spirochaeta cf.aurantia, which could not be detected on normal, broad spectrum bacterial test media. The presence of this bacterial species was detected only by phase contrast and DAPI (4,6-diamidino-2-phenylindole) stained fluorescence microscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02186215
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature tolerances of toxic dinoflagellate cysts: application to the treatment of ships' ballast water (1997)
    Springer
    Aquatic ecology 31 (1997), S. 47-52 
    Details
    ISSN: 1573-5125
    Keywords: toxic dinoflagellates ; temperature tolerance ; ballast water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using toxic dinoflagellates and their resistant resting cysts as model organisms, we demonstrate the potential of heat treatment as a method to minimise the transport of harmful aquatic organisms via ships' ballast water. Vegetative dinoflagellate cultures of Gymnodinium catenatum could be readily killed using temperatures as low as 35 °C and treatment times in the range 30 minutes to 5 h. The resistant resting cysts (hypnozygotes) of G. catenatum were killed after 2 h at 35 °C and the cysts of Alexandrium catenella were killed after 4.5 h at 38 °C . A careful assessment of various waste heat sources on the BHP bulk carrier ‘Iron Whyalla’ has confirmed the practicability of this approach, and a successful pilot heat treatment plant was trialled on-board ship in April 1997.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009972931195
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  • 4
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    Alexandrium diversaporum sp. nov., a new non-saxitoxin producing species: Phylogeny, morphology and sxtA genes (2014)
    ELSEVIER SCIENCE BV
    In:  EPIC3Harmful Algae, ELSEVIER SCIENCE BV, 31, pp. 54-65, ISSN: 1568-9883
    Details
    Publication Date: 2019-07-16
    Description: Species of the PST producing planktonic marine dinoflagellate genus Alexandrium have been intensively scrutinised, and it is therefore surprising that new taxa can still be found. Here we report a new species, Alexandrium diversaporum nov. sp., isolated from spherical cysts found at two sites in Tasmania, Australia. This species differs in its morphology from all previously reported Alexandrium species, possessing a unique combination of morphological features: the presence of 2 size classes of thecal pores on the cell surface, a medium cell size, the size and shape of the 600 , 10 , 20000 and Sp plates, the lack of a ventral pore, a lack of anterior and posterior connecting pores, and a lack of chain formation. We determined the relationship of the two strains to other species of Alexandrium based on an alignment of concatenated SSU-ITS1, 5.8S, ITS2 and partial LSU ribosomal RNA sequences, and found A. diversaporum to be a sister group to Alexandrium leei with high support. A. leei shares several morphological features, including the relative size and shapes of the 600 , 10 , 20000 and Sp plates and the fact that some strains of A. leei have two size classes of thecal pores. We examined A. diversaporum strains for saxitoxin production and found them to be non-toxic. The species lacked sequences for the domain A4 of sxtA, as has been previously found for non-saxitoxin producing species of Alexandrium.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Polyketide synthesis genes associated with toxin production in two species of Gambierdiscus (Dinophyceae) (2015)
    BIOMED CENTRAL LTD
    In:  EPIC3BMC Genomics, BIOMED CENTRAL LTD, 16, pp. 410, ISSN: 1471-2164
    Details
    Publication Date: 2015-07-06
    Description: Background: Marine microbial protists, in particular, dinoflagellates, produce polyketide toxins with ecosystem-wide and human health impacts. Species of Gambierdiscus produce the polyether ladder compounds ciguatoxins and maitotoxins, which can lead to ciguatera fish poisoning, a serious human illness associated with reef fish consumption. Genes associated with the biosynthesis of polyether ladder compounds are yet to be elucidated, however, stable isotope feeding studies of such compounds consistently support their polyketide origin indicating that polyketide synthases are involved in their biosynthesis. Results: Here, we report the toxicity, genome size, gene content and transcriptome of Gambierdiscus australes and G. belizeanus. G. australes produced maitotoxin-1 and maitotoxin-3, while G. belizeanus produced maitotoxin-3, for which cell extracts were toxic to mice by IP injection (LD50 = 3.8 mg kg(-1)). The gene catalogues comprised 83,353 and 84,870 unique contigs, with genome sizes of 32.5 +/- 3.7 Gbp and 35 +/- 0.88 Gbp, respectively, and are amongst the most comprehensive yet reported from a dinoflagellate. We found three hundred and six genes involved in polyketide biosynthesis, including one hundred and ninty-two ketoacyl synthase transcripts, which formed five unique phylogenetic clusters. Conclusions: Two clusters were unique to these maitotoxin-producing dinoflagellate species, suggesting that they may be associated with maitotoxin biosynthesis. This work represents a significant step forward in our understanding of the genetic basis of polyketide production in dinoflagellates, in particular, species responsible for ciguatera fish poisoning.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 6
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    Morphological and phylogenetic data do not support the split of Alexandrium into four genera (2020)
    ELSEVIER SCIENCE BV
    In:  EPIC3Harmful Algae, ELSEVIER SCIENCE BV, 98, pp. 101902, ISSN: 1568-9883
    Details
    Publication Date: 2023-03-13
    Description: A recently published study analyzed the phylogenetic relationship between the genera Centrodinium and Alexandrium, confirming an earlier publication showing the genus Alexandrium as paraphyletic. This most recent manuscript retained the genus Alexandrium, introduced a new genus Episemicolon, resurrected two genera, Gessnerium and Protogonyaulax, and stated that: “The polyphyly [sic] of Alexandrium is solved with the split into four genera”. However, these reintroduced taxa were not based on monophyletic groups. Therefore this work, if accepted, would result in replacing a single paraphyletic taxon with several non-monophyletic ones. The morphological data presented for genus characterization also do not convincingly support taxa delimitations. The combination of weak molecular phylogenetics and the lack of diagnostic traits (i.e., autapomorphies) render the applicability of the concept of limited use. The proposal to split the genus Alexandrium on the basis of our current knowledge is rejected herein. The aim here is not to present an alternative analysis and revision, but to maintain Alexandrium. A better constructed and more phylogenetically accurate revision can and should wait until more complete evidence becomes available and there is a strong reason to revise the genus Alexandrium. The reasons are explained in detail by a review of the available molecular and morphological data for species of the genera Alexandrium and Centrodinium. In addition, cyst morphology and chemotaxonomy are discussed, and the need for integrative taxonomy is highlighted.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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