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Lisa Campbell - One of the best experts on this subject based on the ideXlab platform.
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Origins of Karenia brevis harmful algal blooms along the Texas coast
Limnology and Oceanography: Fluids and Environments, 2013Co-Authors: Kristen M. Thyng, Robert D. Hetland, Marcus T. Ogle, Xiaoqian Zhang, Fei Chen, Lisa CampbellAbstract:The dinoflagellate Karenia brevis is the major harmful algal bloom (HAB) species in the Gulf of Mexico. Given that the rapid appearance of K. brevis cannot be explained by plankton growth alone, advection is likely important in bloom initiation. Forward- and backward-moving numerical surface drifters were employed in a numerical model of the Texas–Louisiana shelf to help determine the basic physical mechanisms explaining sporadic interannual occurrences of K. brevis along the Texas coastline. Results from data analysis from the area show that HAB events occur in years in which there are weaker mean downcoast, along-shore wind speeds. The drifter experiments suggest that southern waters play a role in HAB event initiation, providing an offshore source of cells at the end of summer. As winds switch from upcoast to downcoast in early fall, offshore populations of K. brevis are swept southward by wind-driven currents in years with strong downcoast winds. However, when the downshore wind is weak, shoreward Ekman transport creates a convergent flow near the coast that allows cells to concentrate and initiate a bloom.
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Osmotic stress does trigger brevetoxin production in the dinoflagellate Karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Reagan M. Errera, Lisa CampbellAbstract:Although a number of factors may influence its production, the physiological role of brevetoxin in the dinoflagellate Karenia brevis is still open to debate. Not to be left out of the discussion, Sunda et al. (1) challenge our suggestion that salinity stress may be a possible trigger for brevetoxin production. Their “repeat” of our experiment is not an actual replication (extraction protocols, analytical method, K. brevis isolates, and culturing conditions differed among their three laboratories). Moreover, a number of experimental details, including use of internal standards and preparation of toxin standards, are omitted. Internal standards are important because extraction efficiency varies among samples and could affect results. Nevertheless, both reports show that there is no long-term increase in brevetoxin production after salinity stress (1, 2) and that low-toxin cultures [SP1 (2) and “nontoxic” Wilson (1)] do not increase brevetoxin production in response to hypoosmotic stress.
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Population-genetic structure of the toxic dinoflagellate Karenia brevis from the Gulf of Mexico
Journal of Plankton Research, 2013Co-Authors: Darren W. Henrichs, Mark A. Renshaw, John R. Gold, Lisa CampbellAbstract:Blooms of Karenia brevis, the major bloom-forming dinoflagellate in the Gulf of Mexico, are thought to originate in the eastern Gulf. Single-cell polymerase chain reaction and five microsatellites were used to obtain genotypes for > 1800 cells from 38 samples collected from six bloom events. A consistent pattern of genetic divergence between blooms from Florida and Texas was not detected, which supports the hypothesis of a common origin for blooms of K. brevis in the Gulf of Mexico.
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Genetic diversity among clonal isolates of Karenia brevis as measured with microsatellite markers
Harmful Algae, 2012Co-Authors: Darren W. Henrichs, Mark A. Renshaw, John R. Gold, Lisa CampbellAbstract:Abstract Karenia brevis is the major harmful bloom-forming dinoflagellate in the Gulf of Mexico yet little is known about the intraspecific genetic diversity of this species. Here we describe nine new microsatellite markers and, combined with nine previously described microsatellites, use them to genotype 40 cultured isolates of K. brevis. Genetic diversity identified from cultured isolates was compared with the genetic diversity identified from two field samples to assess how well the current cultures represent the field population. Thirty-nine unique haplotypes were identified from 40 cultured isolates of K. brevis using 18 microsatellite markers. Genetic diversity was similar between cultured isolates and the two field samples. The success of 18 microsatellite markers to distinguish individual isolates supports the use of microsatellites as a genetic tool for diagnostic identification of cultured isolates of K. brevis.
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osmotic stress triggers toxin production by the dinoflagellate Karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Reagan M. Errera, Lisa CampbellAbstract:Abstract With the increase in frequency of harmful algal blooms (HABs) worldwide, a better understanding of the mechanisms that influence toxin production is needed. Karenia brevis, the major HAB dinoflagellate in the Gulf of Mexico, produces potent neurotoxins, known as brevetoxins. Human health is directly impacted by blooms of K. brevis through consumption of shellfish contaminated by accumulated brevetoxins (neurotoxic shellfish poisoning) or from aerosolized brevetoxins in sea spray (reduced respiratory function); however, the reason for brevetoxin production has remained a mystery. Here we show that brevetoxin production increased dramatically in response to osmotic stress in three of the four K. brevis clones examined. By rapidly changing salinity to simulate a shift from oceanic conditions to a decreased salinity typical of coastal conditions, brevetoxin production was triggered. As a result, brevetoxin cell quota increased by >14-fold, while growth rate remained unchanged. Live images of K. brevis cells were also examined to assess changes in cell volume. In the K. brevis Wilson clone, cells responded quickly to hypoosmotic stress by increasing their brevetoxin cell quota from ∼10 to 160 pg of brevetoxin per cell, while cell volume remained stable. In contrast, the K. brevis SP1 clone, which has a consistently low brevetoxin cell quota (<1 pg per cell), was unable to balance the hypoosmotic stress, and although brevetoxin production remained low, average cell volume increased. Our findings close a critical gap in knowledge regarding mechanisms for toxin production in K. brevis by providing an explanation for toxin production in this harmful dinoflagellate.
Frances M. Van Dolah - One of the best experts on this subject based on the ideXlab platform.
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Reply to Errera and Campbell: No, low salinity shock does not increase brevetoxins in Karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: William G Sunda, Leanne J Flewelling, Alina A. Corcoran, Jennifer L. Wolny, Cheska Burleson, Jeanine S Morey, Zhihong Wang, D. Ransom Hardison, Frances M. Van DolahAbstract:Our paper (1) was undertaken to challenge earlier reports that low salinity stress increases brevetoxin production in Karenia brevis (2). Despite independent negative findings by three laboratories (1), Errera and Campbell still assert that low salinity shock increases cellular brevetoxins (3). Their initial report of >14-fold increases (2) lacks experimental controls. Their correction (2) substantially reduces the reported increases to 20–53% but does not address the lack of controls or alter their interpretation. They now (3) refer to results from new experiments that have not yet been published or vetted by peer review. In their rebuttal, they misrepresent data in Sunda et al. (1). For example, they say that “laboratory A also demonstrated increased brevetoxin cell quota in SP3 by ∼15% after 12 d,” but this increase was within the SD of replicate analyses. Indeed, statistical tests showed no significant changes in brevetoxin per cell following low salinity shock in the experiments conducted by our three laboratories (1).
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Transcriptome remodeling associated with chronological aging in the dinoflagellate, Karenia brevis.
Marine genomics, 2011Co-Authors: Jillian G. Johnson, Jeanine S Morey, Marion G. Neely, James C. Ryan, Frances M. Van DolahAbstract:The toxic dinoflagellate, Karenia brevis, forms dense blooms in the Gulf of Mexico that persist for many months in coastal waters, where they can cause extensive marine animal mortalities and human health impacts. The mechanisms that enable cell survival in high density, low growth blooms, and the mechanisms leading to often rapid bloom demise are not well understood. To gain an understanding of processes that underlie chronological aging in this dinoflagellate, a microarray study was carried out to identify changes in the global transcriptome that accompany the entry and maintenance of stationary phase up to the onset of cell death. The transcriptome of K. brevis was assayed using a custom 10,263 feature oligonucleotide microarray from mid-logarithmic growth to the onset of culture demise. A total of 2958 (29%) features were differentially expressed, with the mid-stationary phase timepoint demonstrating peak changes in expression. Gene ontology enrichment analyses identified a significant shift in transcripts involved in energy acquisition, ribosome biogenesis, gene expression, stress adaptation, calcium signaling, and putative brevetoxin biosynthesis. The extensive remodeling of the transcriptome observed in the transition into a quiescent non-dividing phase appears to be indicative of a global shift in the metabolic and signaling requirements and provides the basis from which to understand the process of chronological aging in a dinoflagellate.
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Post-transcriptional regulation of S-phase genes in the dinoflagellate, Karenia brevis.
The Journal of eukaryotic microbiology, 2011Co-Authors: Stephanie A. Brunelle, Frances M. Van DolahAbstract:Karenia brevis is a toxic dinoflagellate responsible for red tides in the Gulf of Mexico. The molecular mechanisms controlling its cell cycle are important to bloom formation because blooms develop through vegetative cell division. This study identifies a suite of conserved S-phase genes in K. brevis-proliferating cell nuclear antigen (PCNA), ribonucleotide reductase 2, replication factor C, and replication protein A-and characterizes their expression at the mRNA and protein level over the cell cycle. In higher eukaryotes, the expression of these genes is controlled by transcription, activated at S-phase entry by the E2F transcription factor, which ensures their timely availability for DNA synthesis. In the dinoflagellate, these transcripts possess a 5'-transspliced leader sequence, which suggests they may be under post-transcriptional control as demonstrated in trypanosomes. Using quantitative polymerase chain reaction (qPCR), we confirmed that their transcript levels are unchanged over the cell cycle. However, their proteins are maximally expressed during S-phase. This suggests their cell-cycle-dependent expression may be achieved at the level of translation and/or stability. Proliferating cell nuclear antigen further undergoes an increase in size of ∼9 kDa that dominates during S-phase. This coincides with a change in its distribution, with prominent staining of chromatin-bound PCNA occurring during S-phase. We hypothesize that the change in the observed size of PCNA is due to post-translational modification. Together, these studies demonstrate post-transcriptional regulation of S-phase genes in K. brevis. Differential expression of these S-phase proteins may be useful in the development of biomarkers to assess bloom growth status in the field.
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Cell cycle behavior of laboratory and field populations of the Florida red tide dinoflagellate, Karenia brevis
Continental Shelf Research, 2008Co-Authors: Frances M. Van Dolah, Tod A. Leighfield, Daniel Kamykowski, Gary J. KirkpatrickAbstract:As a component of the ECOHAB Florida Regional Field Program, this study addresses cell cycle behavior and its importance to bloom formation of the Florida red tide dinoflagellate, Karenia brevis. The cell cycle of K. brevis was first studied by flow cytometry in laboratory batch cultures, and a laboratory mesocosm column, followed by field populations over the 5-year course of the ECOHAB program. Under all conditions studied, K. brevis displayed diel phased cell division with S-phase beginning a minimum of 6 h after the onset of light and continuing for 12–14 h. Mitosis occurred during the dark, and was generally completed by the start of the next day. The timing of cell cycle phases relative to the diel cycle did not differ substantially in bloom populations displaying radically different growth rates (mmin 0.17–0.55) under different day lengths and temperature conditions. The rhythm of cell cycle progression is independent from the rhythm controlling vertical migration, as similar cell cycle distributions are found at all depths of the water column in field samples. The implications of these findings are discussed in light of our current understanding of the dinoflagellate cell cycle and the development of improved models for K. brevis bloom growth. Published by Elsevier Ltd.
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spliced leader rna mediated trans splicing in a dinoflagellate Karenia brevis
Journal of Eukaryotic Microbiology, 2007Co-Authors: Kristy B Lidie, Frances M. Van DolahAbstract:Spliced leader (SL) trans-splicing is a form of mRNA processing originally described in parasitic kinetoplastids. During this reaction, a short RNA sequence is transferred from the 5'-end of an SL transcript to a splice acceptor site on pre-mRNA molecules. Here we report numerous mRNAs from a dinoflagellate, Karenia brevis, which contain an identical leader sequence at their 5'-terminal end. Furthermore, we have isolated a gene from K. brevis encoding a putative SL RNA containing the conserved splice donor site immediately following the leader sequence. A 1,742-bp DNA fragment encoding a K. brevis 5S gene repeat was found to encode the SL RNA gene, as well as a U6 small nuclear RNA (snRNA) gene, and binding sites for the core components of the splicesome (Sm proteins) involved in RNA splicing. Therefore the K. brevis SL RNA appears to be in a genomic arrangement typical of SL genes in a number of species known to mature their mRNAs by trans-splicing. Additionally, we show that the SL gene exists as a stable snRNA and has a predicted secondary structure typical of SL RNAs. The data presented here support the hypothesis that an SL RNA is present in K. brevis and that maturation of a percentage of mRNAs in K. brevis occurs via a trans-splicing process in which a common SL sequence is added to the 5'-end of mature mRNAs. The occurrence of SL trans-splicing in a dinoflagellate extends the known phylogenetic range of this process.
Kristy B Lidie - One of the best experts on this subject based on the ideXlab platform.
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spliced leader rna mediated trans splicing in a dinoflagellate Karenia brevis
Journal of Eukaryotic Microbiology, 2007Co-Authors: Kristy B Lidie, Frances M. Van DolahAbstract:Spliced leader (SL) trans-splicing is a form of mRNA processing originally described in parasitic kinetoplastids. During this reaction, a short RNA sequence is transferred from the 5'-end of an SL transcript to a splice acceptor site on pre-mRNA molecules. Here we report numerous mRNAs from a dinoflagellate, Karenia brevis, which contain an identical leader sequence at their 5'-terminal end. Furthermore, we have isolated a gene from K. brevis encoding a putative SL RNA containing the conserved splice donor site immediately following the leader sequence. A 1,742-bp DNA fragment encoding a K. brevis 5S gene repeat was found to encode the SL RNA gene, as well as a U6 small nuclear RNA (snRNA) gene, and binding sites for the core components of the splicesome (Sm proteins) involved in RNA splicing. Therefore the K. brevis SL RNA appears to be in a genomic arrangement typical of SL genes in a number of species known to mature their mRNAs by trans-splicing. Additionally, we show that the SL gene exists as a stable snRNA and has a predicted secondary structure typical of SL RNAs. The data presented here support the hypothesis that an SL RNA is present in K. brevis and that maturation of a percentage of mRNAs in K. brevis occurs via a trans-splicing process in which a common SL sequence is added to the 5'-end of mature mRNAs. The occurrence of SL trans-splicing in a dinoflagellate extends the known phylogenetic range of this process.
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Spliced Leader RNA‐Mediated trans‐Splicing in a Dinoflagellate, Karenia brevis
The Journal of eukaryotic microbiology, 2007Co-Authors: Kristy B Lidie, Frances M. Van DolahAbstract:Spliced leader (SL) trans-splicing is a form of mRNA processing originally described in parasitic kinetoplastids. During this reaction, a short RNA sequence is transferred from the 5'-end of an SL transcript to a splice acceptor site on pre-mRNA molecules. Here we report numerous mRNAs from a dinoflagellate, Karenia brevis, which contain an identical leader sequence at their 5'-terminal end. Furthermore, we have isolated a gene from K. brevis encoding a putative SL RNA containing the conserved splice donor site immediately following the leader sequence. A 1,742-bp DNA fragment encoding a K. brevis 5S gene repeat was found to encode the SL RNA gene, as well as a U6 small nuclear RNA (snRNA) gene, and binding sites for the core components of the splicesome (Sm proteins) involved in RNA splicing. Therefore the K. brevis SL RNA appears to be in a genomic arrangement typical of SL genes in a number of species known to mature their mRNAs by trans-splicing. Additionally, we show that the SL gene exists as a stable snRNA and has a predicted secondary structure typical of SL RNAs. The data presented here support the hypothesis that an SL RNA is present in K. brevis and that maturation of a percentage of mRNAs in K. brevis occurs via a trans-splicing process in which a common SL sequence is added to the 5'-end of mature mRNAs. The occurrence of SL trans-splicing in a dinoflagellate extends the known phylogenetic range of this process.
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chimeric plastid proteome in the florida red tide dinoflagellate Karenia brevis
Molecular Biology and Evolution, 2006Co-Authors: Tetyana Nosenko, Frances M. Van Dolah, Kristy B Lidie, Erika Lindquist, Jan Fang Cheng, Debashish BhattacharyaAbstract:Current understanding of the plastid proteome comes almost exclusively from studies of plants and red algae. The proteome in these taxa has a relatively simple origin via integration of proteins from a single cyanobacterial primary endosymbiont and the host. However, the most successful algae in marine environments are the chlorophyll c-containing chromalveolates such as diatoms and dinoflagellates that contain a plastid of red algal origin derived via secondary or tertiary endosymbiosis. Virtually nothing is known about the plastid proteome in these taxa. We analyzed expressed sequence tag data from the toxic "Florida red tide" dinoflagellate Karenia brevis that has undergone a tertiary plastid endosymbiosis. Comparative analyses identified 30 nuclear-encoded plastid-targeted proteins in this chromalveolate that originated via endosymbiotic or horizontal gene transfer (HGT) from multiple different sources. We identify a fundamental divide between plant/red algal and chromalveolate plastid proteomes that reflects a history of mixotrophy in the latter group resulting in a highly chimeric proteome. Loss of phagocytosis in the "red" and "green" clades effectively froze their proteomes, whereas chromalveolate lineages retain the ability to engulf prey allowing them to continually recruit new, potentially adaptive genes through subsequent endosymbioses and HGT. One of these genes is an electron transfer protein (plastocyanin) of green algal origin in K. brevis that likely allows this species to thrive under conditions of iron depletion.
Tracy A. Villareal - One of the best experts on this subject based on the ideXlab platform.
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does the red tide dinoflagellate Karenia brevis use allelopathy to outcompete other phytoplankton
Limnology and Oceanography, 2005Co-Authors: Julia Kubanek, Jerome Naar, Melissa K Hicks, Tracy A. VillarealAbstract:Monospecific blooms of phytoplankton can disrupt pelagic communities and negatively affect human health and economies. Interspecific competition may play an important role in promoting blooms, and so we tested (1) whether the outcome of competition between the red tide dinoflagellate Karenia brevis (ex Gymnodinium breve) and 12 cooccurring phytoplankters could be explained by allelopathic effects of compounds released by K. brevis and (2) whether waterborne, lipophilic molecules, including brevetoxins, are involved. Nine of 12 phytoplankton species were suppressed when grown with live K. brevis at bloom concentrations. K. brevis extracellular filtrates or lipophilic extracts of filtrates inhibited six of these nine species, indicating allelopathy. However, these inhibitory effects were weaker than those experienced by competitors exposed to live K. brevis. Brevetoxins at ecologically reasonable waterborne concentrations accounted for the modest inhibition by K. brevis of only one competitor, Skeletonema costatum. The addition of brevetoxins also caused significant autoinhibition, reducing the maximum concentration of K. brevis. Allelopathy is one mechanism by which K. brevis appears to exhibit competitive advantage over some sympatric phytoplankters, although unidentified compounds other than brevetoxins must be involved, in most cases. K. brevis was also susceptible to competitive exclusion by several species, including Odontella aurita and Prorocentrum minimum, known to thrive during K. brevis blooms. Although field experiments are required to assess whether allelopathy plays a fundamental role in bloom dynamics, our results indicate that allelopathy occurs widely but with species-specific consequences.
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Detecting Karenia brevis blooms and algal resuspension in the western Gulf of mexico with satellite ocean color imagery
Harmful Algae, 2005Co-Authors: Timothy T. Wynne, Richard P. Stumpf, Michelle C. Tomlinson, Varis Ransibrahmanakul, Tracy A. VillarealAbstract:Blooms of the toxic dinoflagellate, Karenia brevis, have had detrimental impacts on the coastal Gulf of Mexico for decades. Detection of Karenia brevis blooms uses an ecological approach based on anomalies derived from ocean color imagery. The same anomaly product used in Florida produces frequent false positives on the Texas coast. These failures occurred during wind-driven resuspension events. During these events resuspension of benthic algae significantly increases chlorophyll concentrations in the water, resulting in confusion with normal water column phytoplankton, such as Karenia. A method was developed to separate the resuspended chlorophyll from the water column chlorophyll, decreasing the false positives used with the detection method.
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A historical assessment of Karenia brevis in the western Gulf of Mexico
Harmful Algae, 2003Co-Authors: Hugo A. Magaña, Cindy Contreras, Tracy A. VillarealAbstract:This work examines the historical records of red tides in the western Gulf of Mexico (GOM) as they pertain to the toxic dinoflagellate Karenia brevis(Davis) G. Hansen and Moestrup. K. brevis commonly causes major fish kills, human respiratory distress, and significant economic disruption in the Gulf of Mexico. It can also lead to illness by consumption of contaminated shellfish. The nearly annual blooms that have occurred in Florida in the past several decades have focused most attention on the eastern Gulf of Mexico. There are few published chronological accounts of red tides in the western Gulf of Mexico despite a wealth of information on probable red tide blooms in Mexico during the 17th–19th century. Using these data and more modern records, we present a chronology of K. brevis in the western Gulf of Mexico. A 1879 report of red tide blooms in Veracruz, Mexico in the period 1853–1871 provides a clear description of concurrent fish kills and respiratory irritation, and provides the earliest verifiable account of K. brevis in the Gulf of Mexico. An analysis of the records suggests that Texas has experienced a notable increase in red tide frequency in the years 1996–2000. However, the record is too limited to assign any causes. © 2003 Elsevier Science B.V. All rights reserved.
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No difference found in ribosomal DNA sequences from physiologically diverse clones of Karenia brevis (Dinophyceae) from the Gulf of Mexico
Journal of Plankton Research, 2002Co-Authors: P. Loret, Tracy A. Villareal, Bill Richardson, T. Tengs, H. Singler, P. Mcguire, Steve L. Morton, M. Busman, Lisa CampbellAbstract:Maximum growth rate and toxin content were significantly different among five strains of Karenia brevis isolated from Texas and Florida when grown under identical culture conditions. Sequence analysis of the 18S rRNA gene and internal transcribed spacer (ITS) regions revealed, however, that all five strains were identical. Consequently, a clear genetic basis for physiological variability among various geographical isolates of K. brevis from the Gulf of Mexico could not be assessed using these genetic markers. Both the ITS and 18S rRNA regions may be useful in species-specific probe selection. At the intra-specific level, however, an alternative marker will be needed to assess the diversity among K. brevis populations in the Gulf of Mexico.
Reagan M. Errera - One of the best experts on this subject based on the ideXlab platform.
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Osmotic stress does trigger brevetoxin production in the dinoflagellate Karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Reagan M. Errera, Lisa CampbellAbstract:Although a number of factors may influence its production, the physiological role of brevetoxin in the dinoflagellate Karenia brevis is still open to debate. Not to be left out of the discussion, Sunda et al. (1) challenge our suggestion that salinity stress may be a possible trigger for brevetoxin production. Their “repeat” of our experiment is not an actual replication (extraction protocols, analytical method, K. brevis isolates, and culturing conditions differed among their three laboratories). Moreover, a number of experimental details, including use of internal standards and preparation of toxin standards, are omitted. Internal standards are important because extraction efficiency varies among samples and could affect results. Nevertheless, both reports show that there is no long-term increase in brevetoxin production after salinity stress (1, 2) and that low-toxin cultures [SP1 (2) and “nontoxic” Wilson (1)] do not increase brevetoxin production in response to hypoosmotic stress.
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osmotic stress triggers toxin production by the dinoflagellate Karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Reagan M. Errera, Lisa CampbellAbstract:Abstract With the increase in frequency of harmful algal blooms (HABs) worldwide, a better understanding of the mechanisms that influence toxin production is needed. Karenia brevis, the major HAB dinoflagellate in the Gulf of Mexico, produces potent neurotoxins, known as brevetoxins. Human health is directly impacted by blooms of K. brevis through consumption of shellfish contaminated by accumulated brevetoxins (neurotoxic shellfish poisoning) or from aerosolized brevetoxins in sea spray (reduced respiratory function); however, the reason for brevetoxin production has remained a mystery. Here we show that brevetoxin production increased dramatically in response to osmotic stress in three of the four K. brevis clones examined. By rapidly changing salinity to simulate a shift from oceanic conditions to a decreased salinity typical of coastal conditions, brevetoxin production was triggered. As a result, brevetoxin cell quota increased by >14-fold, while growth rate remained unchanged. Live images of K. brevis cells were also examined to assess changes in cell volume. In the K. brevis Wilson clone, cells responded quickly to hypoosmotic stress by increasing their brevetoxin cell quota from ∼10 to 160 pg of brevetoxin per cell, while cell volume remained stable. In contrast, the K. brevis SP1 clone, which has a consistently low brevetoxin cell quota (<1 pg per cell), was unable to balance the hypoosmotic stress, and although brevetoxin production remained low, average cell volume increased. Our findings close a critical gap in knowledge regarding mechanisms for toxin production in K. brevis by providing an explanation for toxin production in this harmful dinoflagellate.
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Osmotic stress triggers toxin production by the dinoflagellate Karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Reagan M. Errera, Lisa CampbellAbstract:Abstract With the increase in frequency of harmful algal blooms (HABs) worldwide, a better understanding of the mechanisms that influence toxin production is needed. Karenia brevis, the major HAB dinoflagellate in the Gulf of Mexico, produces potent neurotoxins, known as brevetoxins. Human health is directly impacted by blooms of K. brevis through consumption of shellfish contaminated by accumulated brevetoxins (neurotoxic shellfish poisoning) or from aerosolized brevetoxins in sea spray (reduced respiratory function); however, the reason for brevetoxin production has remained a mystery. Here we show that brevetoxin production increased dramatically in response to osmotic stress in three of the four K. brevis clones examined. By rapidly changing salinity to simulate a shift from oceanic conditions to a decreased salinity typical of coastal conditions, brevetoxin production was triggered. As a result, brevetoxin cell quota increased by >14-fold, while growth rate remained unchanged. Live images of K. brevis cells were also examined to assess changes in cell volume. In the K. brevis Wilson clone, cells responded quickly to hypoosmotic stress by increasing their brevetoxin cell quota from ∼10 to 160 pg of brevetoxin per cell, while cell volume remained stable. In contrast, the K. brevis SP1 clone, which has a consistently low brevetoxin cell quota (
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Variation in brevetoxin and brevenal content among clonal cultures of Karenia brevis may influence bloom toxicity.
Toxicon : official journal of the International Society on Toxinology, 2009Co-Authors: Reagan M. Errera, D. W. Henrichs, A Bourdelais, M A Drennan, E B Dodd, L. CampbellAbstract:Karenia brevis, the major harmful algal (HA) species in the Gulf of Mexico, produces a suite of brevetoxins and brevenal, a nontoxic brevetoxin antagonist. K. brevis growth is reported to be optimum at oceanic conditions, yet blooms are most problematic in coastal waters. Differences in growth rate, total brevetoxin production, brevetoxin profiles and brevenal production were evaluated among eight K. brevis clones grown at salinities of 35 and 27, but otherwise identical conditions. All measured parameters varied significantly among clones and the individual responses to decreased salinity varied as well. At 27, growth rates of four clones increased (Wilson, TXB3, SP1 and SP2), but decreased in three others (TXB4, SP3 and NBK) as compared to 35. Total brevetoxin cellular concentration varied up to approximately ten-fold among clones. For most clones (5 of 8), no significant difference in total toxin production between salinity treatments was observed; however, there was a shift in brevetoxin profiles to a higher proportion of PbTx-1 vs. PbTx-2 (in 7 of 8 clones). Brevenal production decreased in the majority of the clones (6 of 8) when grown at a salinity of 27. Results suggest that K. brevis produces more PbTx-1 and less brevenal in lower salinity waters.
