ORCID Profile
0000-0002-7553-9524
Current Organisation
Norwegian Institute of Public Health
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Publisher: Public Library of Science (PLoS)
Date: 18-05-2011
Publisher: Public Library of Science (PLoS)
Date: 19-11-2012
Publisher: American Society for Microbiology
Date: 04-2013
DOI: 10.1128/AEM.03279-12
Abstract: Saxitoxin and its derivatives are potent neurotoxins produced by several cyanobacteria and dinoflagellate species. SxtA is the initial enzyme in the biosynthesis of saxitoxin. The dinoflagellate full mRNA and partial genomic sequences have previously been characterized, and it appears that sxtA originated in dinoflagellates through a horizontal gene transfer from a bacterium. So far, little is known about the remaining genes involved in this pathway in dinoflagellates. Here we characterize sxtG , an amidinotransferase enzyme gene that putatively encodes the second step in saxitoxin biosynthesis. In this study, the entire sxtG transcripts from Alexandrium fundyense CCMP1719 and Alexandrium minutum CCMP113 were lified and sequenced. The transcripts contained typical dinoflagellate spliced leader sequences and eukaryotic poly(A) tails. In addition, partial sxtG transcript fragments were lified from four additional Alexandrium species and Gymnodinium catenatum . The phylogenetic inference of dinoflagellate sxtG , congruent with sxtA , revealed a bacterial origin. However, it is not known if sxtG was acquired independently of sxtA . Amplification and sequencing of the corresponding genomic sxtG region revealed noncanonical introns. These introns show a high interspecies and low intraspecies variance, suggesting multiple independent acquisitions and losses. Unlike sxtA , sxtG was also lified from Alexandrium species not known to synthesize saxitoxin. However, lification was not observed for 22 non-saxitoxin-producing dinoflagellate species other than those of the genus Alexandrium or G. catenatum . This result strengthens our hypothesis that saxitoxin synthesis has been secondarily lost in conjunction with sxtA for some descendant species.
Publisher: MDPI AG
Date: 08-08-2013
DOI: 10.3390/MD11082814
Publisher: American Society for Microbiology
Date: 10-2011
DOI: 10.1128/AEM.05308-11
Abstract: The recent identification of genes involved in the production of the potent neurotoxin and keystone metabolite saxitoxin (STX) in marine eukaryotic phytoplankton has allowed us for the first time to develop molecular genetic methods to investigate the chemical ecology of harmful algal blooms in situ . We present a novel method for detecting and quantifying the potential for STX production in marine environmental s les. Our assay detects a domain of the gene sxtA that encodes a unique enzyme putatively involved in the sxt pathway in marine dinoflagellates, sxtA4 . A product of the correct size was recovered from nine strains of four species of STX-producing Alexandrium and Gymnodinium catenatum and was not detected in the non-STX-producing Alexandrium species, other dinoflagellate cultures, or an environmental s le that did not contain known STX-producing species. However, sxtA4 was also detected in the non-STX-producing strain of Alexandrium tamarense , Tasmanian ribotype. We investigated the copy number of sxtA4 in three strains of Alexandrium catenella and found it to be relatively constant among strains. Using our novel method, we detected and quantified sxtA4 in three environmental blooms of Alexandrium catenella that led to STX uptake in oysters. We conclude that this method shows promise as an accurate, fast, and cost-effective means of quantifying the potential for STX production in marine s les and will be useful for biological oceanographic research and harmful algal bloom monitoring.
No related grants have been discovered for Anke Stüken.