A marine scientist with fundamental research interests in chemical ecology and species interactions, and plankton diversity and biogeography coupled to biological oceanographic processes. The initiation and development of Harmful Algal Blooms in the oceanic context of global change and potential for range expansion are primary research themes.
International Council for the Exploration of the Sea (ICES) Annual Science Conference 2019, 9-12 ... more International Council for the Exploration of the Sea (ICES) Annual Science Conference 2019, 9-12 September 2019 Gothenburg, Sweden.-- 1 page, figures.-- 1 page
International Council for the Exploration of the Sea (ICES) Annual Science Conference 2019, 9-12 ... more International Council for the Exploration of the Sea (ICES) Annual Science Conference 2019, 9-12 September 2019 Gothenburg, Sweden.-- 1 page
Cylindrospermopsis raciborskii and Raphidiopsis sp. are filamentous freshwater bloom forming cyan... more Cylindrospermopsis raciborskii and Raphidiopsis sp. are filamentous freshwater bloom forming cyanobacteria, which can co-exist in the same bloom, morphologically distinguishable because of the terminal heterocyst (N fixation cells) in C. raciborskii. C. raciborskii comprise strains which produce either Cylindrospermopsin (CYN) an hepatotoxin, Paralytic Shellfish Poisoning toxins (PSP toxins) or do not produce toxins. On the other hand, the few strains described from Raphidiopsis genus produce anatoxin-a (neurotoxin), CYN, or do not produce toxins. Regardless of these phenotypic differences, C. raciborskii and Raphidiopsis sp. are not differentiable at 16S rRNA sequence level (similarity higher than 99%). However, analysis of the 16S23S rRNA Internal Transcribed Spacer (ITS), from C. raciborskii strains (CYN-producing or non toxic) and one PSP toxin-producing strain morphologically classified as C. raciborskii strain D9 showed a 28bp deletion signature of Raphidiopsis strains in D9. ...
Background: The dinoflagellate Alexandrium minutum typically produces paralytic shellfish poisoni... more Background: The dinoflagellate Alexandrium minutum typically produces paralytic shellfish poisoning (PSP) toxins, which are known only from cyanobacteria and dinoflagellates. While a PSP toxin gene cluster has recently been characterized in cyanobacteria, the genetic background of PSP toxin production in dinoflagellates remains elusive. Results: We constructed and analysed an expressed sequence tag (EST) library of A. minutum, which contained 15,703 read sequences yielding a total of 4,320 unique expressed clusters. Of these clusters, 72% combined the forward-and reverse reads of at least one bacterial clone. This sequence resource was then used to construct an oligonucleotide microarray. We analysed the expression of all clusters in three different strains. While the cyanobacterial PSP toxin genes were not found among the A. minutum sequences, 192 genes were differentially expressed between toxic and non-toxic strains. Conclusions: Based on this study and on the lack of identified PSP synthesis genes in the two existent Alexandrium tamarense EST libraries, we propose that the PSP toxin genes in dinoflagellates might be more different from their cyanobacterial counterparts than would be expected in the case of a recent gene transfer. As a starting point to identify possible PSP toxin-associated genes in dinoflagellates without relying on a priori sequence information, the sequences only present in mRNA pools of the toxic strain can be seen as putative candidates involved in toxin synthesis and regulation, or acclimation to intracellular PSP toxins.
Emerging phylogeographic perspective on the toxigenic diatom genus Pseudo-nitzschia in coastal northern European waters and gateways to eastern Arctic seas, 2023
International Council for the Exploration of the Sea (ICES) Annual Science Conference 2019, 9-12 ... more International Council for the Exploration of the Sea (ICES) Annual Science Conference 2019, 9-12 September 2019 Gothenburg, Sweden.-- 1 page, figures.-- 1 page
International Council for the Exploration of the Sea (ICES) Annual Science Conference 2019, 9-12 ... more International Council for the Exploration of the Sea (ICES) Annual Science Conference 2019, 9-12 September 2019 Gothenburg, Sweden.-- 1 page
Cylindrospermopsis raciborskii and Raphidiopsis sp. are filamentous freshwater bloom forming cyan... more Cylindrospermopsis raciborskii and Raphidiopsis sp. are filamentous freshwater bloom forming cyanobacteria, which can co-exist in the same bloom, morphologically distinguishable because of the terminal heterocyst (N fixation cells) in C. raciborskii. C. raciborskii comprise strains which produce either Cylindrospermopsin (CYN) an hepatotoxin, Paralytic Shellfish Poisoning toxins (PSP toxins) or do not produce toxins. On the other hand, the few strains described from Raphidiopsis genus produce anatoxin-a (neurotoxin), CYN, or do not produce toxins. Regardless of these phenotypic differences, C. raciborskii and Raphidiopsis sp. are not differentiable at 16S rRNA sequence level (similarity higher than 99%). However, analysis of the 16S23S rRNA Internal Transcribed Spacer (ITS), from C. raciborskii strains (CYN-producing or non toxic) and one PSP toxin-producing strain morphologically classified as C. raciborskii strain D9 showed a 28bp deletion signature of Raphidiopsis strains in D9. ...
Background: The dinoflagellate Alexandrium minutum typically produces paralytic shellfish poisoni... more Background: The dinoflagellate Alexandrium minutum typically produces paralytic shellfish poisoning (PSP) toxins, which are known only from cyanobacteria and dinoflagellates. While a PSP toxin gene cluster has recently been characterized in cyanobacteria, the genetic background of PSP toxin production in dinoflagellates remains elusive. Results: We constructed and analysed an expressed sequence tag (EST) library of A. minutum, which contained 15,703 read sequences yielding a total of 4,320 unique expressed clusters. Of these clusters, 72% combined the forward-and reverse reads of at least one bacterial clone. This sequence resource was then used to construct an oligonucleotide microarray. We analysed the expression of all clusters in three different strains. While the cyanobacterial PSP toxin genes were not found among the A. minutum sequences, 192 genes were differentially expressed between toxic and non-toxic strains. Conclusions: Based on this study and on the lack of identified PSP synthesis genes in the two existent Alexandrium tamarense EST libraries, we propose that the PSP toxin genes in dinoflagellates might be more different from their cyanobacterial counterparts than would be expected in the case of a recent gene transfer. As a starting point to identify possible PSP toxin-associated genes in dinoflagellates without relying on a priori sequence information, the sequences only present in mRNA pools of the toxic strain can be seen as putative candidates involved in toxin synthesis and regulation, or acclimation to intracellular PSP toxins.
Emerging phylogeographic perspective on the toxigenic diatom genus Pseudo-nitzschia in coastal northern European waters and gateways to eastern Arctic seas, 2023
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Papers by Allan Cembella