Publications by authors named "Allen Place"

64 Publications

Spatiotemporal distribution of phycotoxins and their co-occurrence within nearshore waters.

Harmful Algae 2021 03 10;103:101993. Epub 2021 Feb 10.

Virginia Institute of Marine Science, William & Mary, Gloucester Point, VA 23062, USA. Electronic address:

Harmful algal blooms (HABs), varying in intensity and causative species, have historically occurred throughout the Chesapeake Bay, U.S.; however, phycotoxin data are sparse. The spatiotemporal distribution of phycotoxins was investigated using solid-phase adsorption toxin tracking (SPATT) across 12 shallow, nearshore sites within the lower Chesapeake Bay and Virginia's coastal bays over one year (2017-2018). Eight toxins, azaspiracid-1 (AZA1), azaspiracid-2 (AZA2), microcystin-LR (MC-LR), domoic acid (DA), okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-2 (PTX2), and goniodomin A (GDA) were detected in SPATT extracts. Temporally, phycotoxins were always present in the region, with at least one phycotoxin group (i.e., consisting of OA and DTX1) detected at every time point. Co-occurrence of phycotoxins was also common; two or more toxin groups were observed in 76% of the samples analyzed. Toxin maximums: 0.03 ng AZA2/g resin/day, 0.25 ng DA/g resin/day, 15 ng DTX1/g resin/day, 61 ng OA/g resin/day, 72 ng PTX2/g resin/day, and 102,050 ng GDA/g resin/day were seasonal, with peaks occurring in summer and fall. Spatially, the southern tributary and coastal bay regions harbored the highest amount of total phycotoxins on SPATT over the year, and the former contained the greatest diversity of phycotoxins. The novel detection of AZAs in the region, before a causative species has been identified, supports the use of SPATT as an explorative tool in respect to emerging threats. The lack of karlotoxin in SPATT extracts, but detection of Karlodinium veneficum by microscopy, however, emphasizes that this tool should be considered complementary to, but not a replacement for, more traditional HAB management and monitoring methods.
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http://dx.doi.org/10.1016/j.hal.2021.101993DOI Listing
March 2021

A Screening Tool for the Direct Analysis of Marine and Freshwater Phycotoxins in Organic SPATT Extracts from the Chesapeake Bay.

Toxins (Basel) 2020 05 13;12(5). Epub 2020 May 13.

Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA 23062, USA.

Many detection methods for phycotoxins, bioactive compounds produced by harmful algae, focus on one compound or a class of related compounds. Multiple harmful algal species often co-occur in the environment, however, emphasizing the need to analyze for the presence of multiple groups of marine and freshwater phycotoxins in environmental samples, e.g., extracts from solid phase adsorption toxin tracking (SPATT). Two methods were developed to screen for 13 phycotoxins (microcystin-RR, -LR, -YR, azaspiracid-1, -2, karlotoxin 3, goniodomin A, brevetoxin-2, yessotoxin, pectenotoxin-2, dinophysistoxin-1, -2, and okadaic acid) in organic SPATT extracts using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) equipped with a trapping dimension (trap) and at-column dilution (ACD). The performance of each compound under 36 combinations of chromatographic conditions was characterized, and two final methods, acidic and basic, were selected based on peak shapes, signal intensities, resolution, and the separation in time of positive and negative MS ionization modes. Injection volumes of up to 1 mL were possible through trap/ACD technology, resulting in limits of detection between 0.001 and 0.05 µg/L across the analytes. Benefits highlighted in this study, beyond the improved detection limits and co-detection of multiple toxin groups, include the ability to inject samples of 100% organic solvent, ensuring analyte stability and streamlining workflow through the elimination of laborious sample preparation steps.
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http://dx.doi.org/10.3390/toxins12050322DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7290987PMC
May 2020

Effects of dietary taurine level on visual function in European sea bass (Dicentrarchus labrax).

PLoS One 2019 18;14(6):e0214347. Epub 2019 Jun 18.

Center for Veterinary Medicine, U.S. Food and Drug Administration, Rockville, Maryland, United States of America.

Dietary insufficiencies have been well documented to decrease growth rates and survival (and therefore overall production) in fish aquaculture. By contrast, the effects of dietary insufficiencies on the sensory biology of cultured fish remains largely unstudied. Diets based solely on plant protein sources could have advantages over fish-based diets because of the cost and ecological effects of the latter, but plant proteins lack the amino acid taurine. Adequate levels of taurine are, however, necessary for the development of a fully functional visual system in mammals. As part of ongoing studies to determine the suitability of plant-based diets, we investigated the effects of normal and reduced taurine dietary levels on retinal anatomy and function in European sea bass (Dicentrarchus labrax). We could not demonstrate any effects of dietary taurine level on retinal anatomy, nor the functional properties of luminous sensitivity and temporal resolution (measured as flicker fusion frequency). We did, however, find an effect on spectral sensitivity. The peak of spectral sensitivity of individuals fed a 5% taurine diet was rightward shifted (i.e., towards longer wavelengths) relative to that of fish fed a 0% or 1.5% taurine diet. This difference in in spectral sensitivity was due to a relatively lower level of middle wavelength pigment (maximum absorbance .500 nm) in fish fed a 5% taurine diet. Changes in spectral sensitivity resulting from diets containing different taurine levels are unlikely to be detrimental to fish destined for market, but could be in fishes that are being reared for stock enhancement programs.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0214347PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6581246PMC
January 2020

The chemodiversity of algal dissolved organic matter from lysed Microcystis aeruginosa cells and its ability to form disinfection by-products during chlorination.

Water Res 2019 May 27;155:300-309. Epub 2019 Feb 27.

Helmholtz Zentrum Muenchen, Research Unit Analytical BioGeoChemistry, Neuherberg, Germany; Technische Universität München, Chair of Analytical Food Chemistry, Freising-Weihenstephan, Germany.

Algal-derived dissolved organic matter (ADOM) originating from lysed Microcystis aeruginosa cells was investigated as precursor material to form disinfection by-products upon disinfection with free chlorine. Non-targeted ultrahigh resolution 12 T negative mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed high molecular diversity in solid-phase extracted and ionizable components of Microcystis aeruginosa ADOM. The toxin microcystin LR was effectively degraded by free chlorine, which was expected. However, we found a high diversity of disinfection by-products associated with the addition of free chlorine to the water-soluble and solid-phase extractable fraction of ADOM and of double-bond moieties in abundant and known unsaturated fatty acids. Aromatic DOM precursors were absent from known metabolites of Microcystis aeruginosa and no evidence for aromatic disinfection by-products (DBPs) was found, despite N-containing compounds. A large diversification of N-containing molecular formulas was observed after chlorination, which seems indicative for the breakdown and oxidation of larger peptides. Additionally, a diverse group of N-compounds with presumed chloramine functional groups was observed. This study highlights the importance to evaluate ADOM and its ability to form different DBPs when compared to allochthonous or terrestrially-derived DOM.
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http://dx.doi.org/10.1016/j.watres.2019.02.030DOI Listing
May 2019

LC-MS/MS Detection of Karlotoxins Reveals New Variants in Strains of the Marine Dinoflagellate Karlodinium veneficum from the Ebro Delta (NW Mediterranean).

Mar Drugs 2017 Dec 18;15(12). Epub 2017 Dec 18.

Institute of Marine and Environmental Technology, UMCES, Baltimore, MD 21613, USA.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the detection and quantitation of karlotoxins in the selected reaction monitoring (SRM) mode. This novel method was based upon the analysis of purified karlotoxins (KcTx-1, KmTx-2, 44-oxo-KmTx-2, KmTx-5), one amphidinol (AM-18), and unpurified extracts of bulk cultures of the marine dinoflagellate strain CCMP2936 from Delaware (Eastern USA), which produces KmTx-1 and KmTx-3. The limit of detection of the SRM method for KmTx-2 was determined as 2.5 ng on-column. Collision induced dissociation (CID) spectra of all putative karlotoxins were recorded to present fragmentation patterns of each compound for their unambiguous identification. Bulk cultures of strain K10 isolated from an embayment of the Ebro Delta, NW Mediterranean, yielded five previously unreported putative karlotoxins with molecular masses 1280, 1298, 1332, 1356, and 1400 Da, and similar fragments to KmTx-5. Analysis of several isolates of from the Ebro Delta revealed small-scale diversity in the karlotoxin spectrum in that one isolate from Fangar Bay produced KmTx-5, whereas the five putative novel karlotoxins were found among several isolates from nearby, but hydrographically distinct Alfacs Bay. Application of this LC-MS/MS method represents an incremental advance in the determination of putative karlotoxins, particularly in the absence of a complete spectrum of purified analytical standards of known specific potency.
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http://dx.doi.org/10.3390/md15120391DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5742851PMC
December 2017

Assimilation efficiency of sediment-bound PCBs ingested by fish impacted by strong sorption.

Environ Toxicol Chem 2017 12 17;36(12):3480-3488. Epub 2017 Oct 17.

Department of Chemical, Biochemical, and Environmental Engineering, University of Maryland Baltimore County, Baltimore, Maryland, USA.

Uptake of polychlorinated biphenyls (PCBs) by fish is controlled by the bioavailability of ingested PCBs in the gut and the freely dissolved concentration in the water moving across the gills. The prediction of bioaccumulation in fish relies on models that account for these exposure routes; however, these models typically do not account for incidental ingestion of sediment by fish, which is not well studied. The literature values for the PCB assimilation efficiency in the gut have been reported for compounds in food matrices and not associated with sediment particles. It is also unclear how mitigation strategies that alter PCB bioavailability in sediments affect predictions made by the bioaccumulation models when sediment ingestion is involved. To test the bioavailability of PCBs from treated and untreated sediments, dietary assimilation efficiencies were measured for 16 PCB congeners in mummichogs (Fundulus heteroclitus) that were fed 4 experimental diets. Diets consisted of PCB-spiked earthworms, spiked untreated sediment mixed with earthworms, spiked activated carbon-treated sediment mixed with earthworms, and spiked activated carbon mixed with earthworms. Assimilation efficiencies were determined by calculating the ratio of PCB mass in the fish tissue to the PCB mass in the food after a pulse feeding experiment. Assimilation efficiencies of PCBs associated with earthworm diet were similar to the values reported in the literature. Fish that were fed the PCB-spiked untreated sediment and activated carbon particles exhibited the highest and lowest assimilation efficiencies, respectively, over a wide K range. Assimilation efficiencies of sediment-bound PCBs were significantly reduced (31-93% reduction for different congeners) after amendment with activated carbon. The present study indicates that assimilation of PCBs can be reduced by sorption to black carbon. Environ Toxicol Chem 2017;36:3480-3488. © 2017 SETAC.
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http://dx.doi.org/10.1002/etc.3932DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5705292PMC
December 2017

Use of Antibiotics for Maintenance of Axenic Cultures of Amphidinium carterae for the Analysis of Translation.

Mar Drugs 2017 08 1;15(8). Epub 2017 Aug 1.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, 701 E. Pratt Street, Baltimore, MD 21202, USA.

Most dinoflagellates in culture are bacterized, complicating the quantification of protein synthesis, as well as the analysis of its regulation. In bacterized cultures of Hulbert, up to 80% of protein synthetic activity appears to be predominantly bacterial based on responses to inhibitors of protein synthesis. To circumvent this, axenic cultures of were obtained and shown to respond to inhibitors of protein synthesis in a manner characteristic of eukaryotes. However, these responses changed with time in culture correlating with the reappearance of bacteria. Here we show that culture with kanamycin (50 μg/mL), carbenicillin (100 μg/mL), and streptomycin sulfate (50 μg/mL) (KCS), but not 100 units/mL of penicillin and streptomycin (PS), prevents the reappearance of bacteria and allows protein synthesis to be quantified without the contribution of an associated bacterial community. We demonstrate that can grow in the absence of a bacterial community. Furthermore, maintenance in KCS does not inhibit the growth of cultures but slightly extends the growth phase and allows accumulation to somewhat higher saturation densities. We also show that cultures of maintained in KCS respond to the eukaryotic protein synthesis inhibitors cycloheximide, emetine, and harringtonine. Establishment of these culture conditions will facilitate our ability to use polysome fractionation and ribosome profiling to study mRNA recruitment. Furthermore, this study shows that a simple and fast appraisal of the presence of a bacterial community in cultures can be made by comparing responses to cycloheximide and chloramphenicol rather than depending on lengthier culture-based assessments.
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http://dx.doi.org/10.3390/md15080242DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577597PMC
August 2017

Toxin-Antitoxin Systems in Estuarine Strain CB0101 and Their Transcriptomic Responses to Environmental Stressors.

Front Microbiol 2017 6;8:1213. Epub 2017 Jul 6.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, BaltimoreMD, United States.

Bacterial toxin-antitoxin (TA) systems are genetic elements composed of a toxin gene and its cognate antitoxin, with the ability to regulate growth. TA systems have not previously been reported in marine or . Here we report the finding of seven TA system pairs (Type II) in the estuarine CB0101, and their responses of these TA genes to under different stress conditions, which include; nitrogen and phosphate starvation, phage infection, zinc toxicity, and photo-oxidation. Database searches discovered that eight other marine strains also contain at least one TA pair but none were found in . We demonstrate that the TA pair was active and resulted in RNA degradation when CB0101 was under oxidative stress caused by either zinc toxicity or high light intensities, but the growth inhibition was released when the stress was removed. Having TA systems allows CB0101 to adapt to the low light and highly variable environments in the Chesapeake Bay. We propose that TA systems could be more important for picocyanobacteria living in the freshwater and estuarine environments compared to those living in the open ocean.
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http://dx.doi.org/10.3389/fmicb.2017.01213DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5498466PMC
July 2017

Running the Stop Sign: Readthrough of a Premature UAG Termination Signal in the Translation of a Zebrafish (Danio rerio) Taurine Biosynthetic Enzyme.

Mar Drugs 2017 Jun 3;15(6). Epub 2017 Jun 3.

Institute of Marine and Environmental Technology, 701 E. Pratt Street, Baltimore, MD 21202, USA.

The UAG termination codon is generally recognized as the least efficient and least frequently used of the three universal stop codons. This is substantiated by numerous studies in an array of organisms. We present here evidence of a translational readthrough of a mutant nonsense UAG codon in the transcript from the cysteine sulfinic acid decarboxylase () gene (ENSDARG00000026348) in zebrafish. The gene encodes the terminal enzyme in the taurine biosynthetic pathway. Taurine is a critical amino acid for all animals, playing several essential roles throughout the body, including modulation of the immune system. The sa9430 zebrafish strain (ZDB-ALT-130411-5055) has a point mutation leading to a premature stop codon (UAG) 20 amino acids 5' of the normal stop codon, UGA. Data from immunoblotting, enzyme activity assays, and mass spectrometry provide evidence that the mutant is making a CSAD protein identical to that of the wild-type (XP_009295318.1) in terms of size, activity, and amino acid sequence. UAG readthrough has been described in several species, but this is the first presentation of a case in fish. Also presented are the first data substantiating the ability of a fish CSAD to utilize cysteic acid, an alternative to the standard substrate cysteine sulfinic acid, to produce taurine.
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http://dx.doi.org/10.3390/md15060162DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484112PMC
June 2017

Characterization of Acetyl-CoA Carboxylases in the Basal Dinoflagellate Amphidinium carterae.

Mar Drugs 2017 May 26;15(6). Epub 2017 May 26.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, MD 21201, USA.

Dinoflagellates make up a diverse array of fatty acids and polyketides. A necessary precursor for their synthesis is malonyl-CoA formed by carboxylating acetyl CoA using the enzyme acetyl-CoA carboxylase (ACC). To date, information on dinoflagellate ACC is limited. Through transcriptome analysis in we found three full-length homomeric type ACC sequences; no heteromeric type ACC sequences were found. We assigned the putative cellular location for these ACCs based on transit peptide predictions. Using streptavidin Western blotting along with mass spectrometry proteomics, we validated the presence of ACC proteins. Additional bands showing other biotinylated proteins were also observed. Transcript abundance for these ACCs follow the global pattern of expression for dinoflagellate mRNA messages over a diel cycle. This is one of the few descriptions at the transcriptomic and protein level of ACCs in dinoflagellates. This work provides insight into the enzymes which make the CoA precursors needed for fatty acid and toxin synthesis in dinoflagellates.
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http://dx.doi.org/10.3390/md15060149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484099PMC
May 2017

Taurine Biosynthesis in a Fish Liver Cell Line (ZFL) Adapted to a Serum-Free Medium.

Mar Drugs 2017 May 25;15(6). Epub 2017 May 25.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, 701 E. Pratt Street, Baltimore, MD 21202, USA.

Although taurine has been shown to play multiple important physiological roles in teleosts, little is known about the molecular mechanisms underlying dietary requirements. Cell lines can provide useful tools for deciphering biosynthetic pathways and their regulation. However, culture media and sera contain variable taurine levels. To provide a useful cell line for the investigation of taurine homeostasis, an adult zebrafish liver cell line (ZFL) has been adapted to a taurine-free medium by gradual accommodation to a commercially available synthetic medium, UltraMEM™-ITES. Here we show that ZFL cells are able to synthesize taurine and be maintained in medium without taurine. This has allowed for the investigation of the effects of taurine supplementation on cell growth, cellular amino acid pools, as well as the expression of the taurine biosynthetic pathway and taurine transporter genes in a defined fish cell type. After taurine supplementation, cellular taurine levels increase but hypotaurine levels stay constant, suggesting little suppression of taurine biosynthesis. Cellular methionine levels do not change after taurine addition, consistent with maintenance of taurine biosynthesis. The addition of taurine to cells grown in taurine-free medium has little effect on transcript levels of the biosynthetic pathway genes for cysteine dioxygenase (CDO), cysteine sulfinate decarboxylase (CSAD), or cysteamine dioxygenase (ADO). In contrast, supplementation with taurine causes a 30% reduction in transcript levels of the taurine transporter, TauT. This experimental approach can be tailored for the development of cell lines from aquaculture species for the elucidation of their taurine biosynthetic capacity.
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http://dx.doi.org/10.3390/md15060147DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484097PMC
May 2017

qPCR assays for and (Dinophyceae) identified from Alaskan waters and a review of species-specific molecular assays.

Phycologia 2017 May;56(3):303-320

NCCOS/NOAA, Center for Coastal Fisheries and Habitat Research, 101 Pivers Island Road, Beaufort, North Carolina 28516, USA.

Paralytic shellfish poisoning (PSP) poses a serious health threat in Alaska and prevents effective utilization of shellfish resources by subsistence and recreational harvesters. Substantial economic losses also affect shellfish growers during PSP events. The toxins responsible for PSP are produced by dinoflagellates in the genus Despite the persistent threat posed by PSP and the long history of shellfish toxicity research, there is still confusion concerning the species that cause PSP in Alaska. The primary objective of this study was to identify the toxic species present in Alaska and to develop polymerase chain reaction (PCR) assays for use in screening phytoplankton and sediment samples. Before developing the PCR assays for this study, we evaluated published assays and many were not adequate because of primer dimer formation or because of cross-reactivity. Rather than continue to grapple with the uncertainty and inadequacy of published assays, we developed new assays for the species most likely to be present in Alaska. Only Group I and were identified from four sampling regions from southeast Alaska to Kodiak Island, indicating that these two species are widely distributed. PCR assays for these two species were converted to quantitative (q)PCR format for use in monitoring programs. During the course of this study, we realized that a systematic evaluation of all published (~150) species-specific assays would be of benefit. Toward this objective, we collated published PCR, qPCR, and hybridization assay primers and probes that targeted the small-subunit (SSU), internal transcribed spacer (ITS/5.8S), or D1-D3 large-subunit (LSU) (SSU/ITS/LSU) ribosomal DNA genes. Each individual primer or probe was screened against the GenBank database and gene sequence alignments constructed as part of this study. These data were used to identify a suite of species-specific assays that can be recommended for evaluation by the global harmful algal bloom community.
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http://dx.doi.org/10.2216/16-41.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7441911PMC
May 2017

Transcriptome Analysis of Core Dinoflagellates Reveals a Universal Bias towards "GC" Rich Codons.

Mar Drugs 2017 Apr 27;15(5). Epub 2017 Apr 27.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, 701 East Pratt St., Baltimore, MD 21202, USA.

Although dinoflagellates are a potential source of pharmaceuticals and natural products, the mechanisms for regulating and producing these compounds are largely unknown because of extensive post-transcriptional control of gene expression. One well-documented mechanism for controlling gene expression during translation is codon bias, whereby specific codons slow or even terminate protein synthesis. Approximately 10,000 annotatable genes from fifteen "core" dinoflagellate transcriptomes along a range of overall guanine and cytosine (GC) content were used for codonW analysis to determine the relative synonymous codon usage (RSCU) and the GC content at each codon position. GC bias in the analyzed dataset and at the third codon position varied from 51% and 54% to 66% and 88%, respectively. Codons poor in GC were observed to be universally absent, but bias was most pronounced for codons ending in uracil followed by adenine (UA). GC bias at the third codon position was able to explain low abundance codons as well as the low effective number of codons. Thus, we propose that a bias towards codons rich in GC bases is a universal feature of core dinoflagellates, possibly relating to their unique chromosome structure, and not likely a major mechanism for controlling gene expression.
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http://dx.doi.org/10.3390/md15050125DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5450531PMC
April 2017

Sponge symbioses between Xestospongia deweerdtae and Plakortis spp. are not motivated by shared chemical defense against predators.

PLoS One 2017 18;12(4):e0174816. Epub 2017 Apr 18.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland, United States of America.

The recently described epizoic sponge-sponge symbioses between Xestospongia deweerdtae and two species of Plakortis present an unusual series of sponge interactions. Sponges from the genus Plakortis are fierce allelopathic competitors, rich in cytotoxic secondary metabolites, and yet X. deweerdtae flourishes as an epizoic encrustation on Plakortis deweerdtaephila and Plakortis symbiotica. Our objective in this study was to evaluate the hypothesis that X. deweerdtae grows epizoic to these two species of Plakortis due to a shared chemical defense against predators. We collected free-living individuals of X. deweerdtae and symbiotic pairs from a wide geographical range to generate crude organic extracts and a series of polarity fractions from sponge extract. We tested the deterrency of these extracts against three common coral reef predators: the bluehead wrasse, Thalassoma bifasciatum, the Caribbean sharpnose puffer, Canthigaster rostrata, and the white spotwrist hermit crab, Pagurus criniticornis. While the chemical defenses of P. deweerdtaephila and P. symbiotica are more potent than those of X. deweerdtae, all of the sponge species we tested significantly deterred feeding in all three generalist predators. The free-living form of X. deweerdtae is mostly defended across the region, with a few exceptions. The associated form of X. deweerdtae is always defended, and both species of Plakortis are very strongly defended, with puffers refusing to consume extract-treated pellets until the extract was diluted to 1/256× concentration. Using diode-array high performance liquid chromatography (HPLC) coupled with high-resolution mass spectrometry (LC-MS/IT-TOF), we found two secondary metabolites from P. deweerdtaephila, probably the cyclic endoperoxides plakinic acid I and plakinic acid K, in low concentrations in the associated-but not the free-living-form of X. deweerdtae, suggesting a possible translocation of defensive chemicals from the basibiont to the epibiont. Comparing the immense deterrency of Plakortis spp. extracts to the extracts of X. deweerdtae gives the impression that there may be some sharing of chemical defenses: one partner in the symbiosis is clearly more defended than the other and a small amount of its defensive chemistry may translocate to the partner. However, X. deweerdtae effectively deters predators with its own defensive chemistry. Multiple lines of evidence provide no support for the shared chemical defense hypothesis. Given the diversity of other potential food resources available to predators on coral reefs, it is improbable that the evolution of these specialized sponge-sponge symbioses has been driven by predation pressure.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0174816PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5395162PMC
May 2017

Karmitoxin: An Amine-Containing Polyhydroxy-Polyene Toxin from the Marine Dinoflagellate Karlodinium armiger.

J Nat Prod 2017 05 5;80(5):1287-1293. Epub 2017 Apr 5.

Department of Biotechnology and Biomedicine, Technical University of Denmark , Søltofts Plads Building 221, DK-2800 Kgs. Lyngby, Denmark.

Marine algae from the genus Karlodinium are known to be involved in fish-killing events worldwide. Here we report for the first time the chemistry and bioactivity of a natural product from the newly described mixotrophic dinoflagellate Karlodinium armiger. Our work describes the isolation and structural characterization of a new polyhydroxy-polyene named karmitoxin. The structure elucidation work was facilitated by use of C enrichment and high-field 2D NMR spectroscopy, where H-C long-range correlations turned out to be very informative. Karmitoxin is structurally related to amphidinols and karlotoxins; however it differs by containing the longest carbon-carbon backbone discovered for this class of compounds, as well as a primary amino group. Karmitoxin showed potent nanomolar cytotoxic activity in an RTgill-W1 cell assay as well as rapid immobilization and eventual mortality of the copepod Acartia tonsa, a natural grazer of K. armiger.
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http://dx.doi.org/10.1021/acs.jnatprod.6b00860DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6446557PMC
May 2017

Identification of a vacuolar proton channel that triggers the bioluminescent flash in dinoflagellates.

PLoS One 2017 8;12(2):e0171594. Epub 2017 Feb 8.

Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, Georgia, United States of America.

In 1972, J. Woodland Hastings and colleagues predicted the existence of a proton selective channel (HV1) that opens in response to depolarizing voltage across the vacuole membrane of bioluminescent dinoflagellates and conducts protons into specialized luminescence compartments (scintillons), thereby causing a pH drop that triggers light emission. HV1 channels were subsequently identified and demonstrated to have important functions in a multitude of eukaryotic cells. Here we report a predicted protein from Lingulodinium polyedrum that displays hallmark properties of bona fide HV1, including time-dependent opening with depolarization, perfect proton selectivity, and characteristic ΔpH dependent gating. Western blotting and fluorescence confocal microscopy of isolated L. polyedrum scintillons immunostained with antibody to LpHV1 confirm LpHV1's predicted organellar location. Proteomics analysis demonstrates that isolated scintillon preparations contain peptides that map to LpHV1. Finally, Zn2+ inhibits both LpHV1 proton current and the acid-induced flash in isolated scintillons. These results implicate LpHV1 as the voltage gated proton channel that triggers bioluminescence in L. polyedrum, confirming Hastings' hypothesis. The same channel likely mediates the action potential that communicates the signal along the tonoplast to the scintillon.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0171594PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5298346PMC
August 2017

Two new karlotoxins found in Karlodinium veneficum (strain GM2) from the East China Sea.

Harmful Algae 2016 09 27;58:66-73. Epub 2016 Aug 27.

Center for Collaborative Innovation, Ningbo University, Ningbo 315211, China; Key Laboratory of Applied Marine Biotechnology (Ningbo University), Ministry of Education, Ningbo 315211, China. Electronic address:

The dinoflagellate Karlodinium veneficum is a harmful algal bloom species with a worldwide distribution. This small athecate dinoflagellate makes a family of polyketide toxins that are hemolytic, cytotoxic and ichthyotoxic. The first chemical structure for karlotoxins from East China Sea (ECS) is reported here. The two new karlotoxins, namely 4,5-dihydro-KmTx 2 (compound 1) and 4,5-dihydro-dechloro-KmTx 2 (compound 2), were isolated and purified from monoalgal cultures of K. veneficum strain GM2. Their structures were determined by spectroscopic analysis, including tandem mass spectrometry as well as 1D and 2D NMR experiments. These new karlotoxin congeners feature a saturated polyol arm different from previously reported for KmTx 2 that appears to increase hemolytic activity.
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http://dx.doi.org/10.1016/j.hal.2016.08.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5228562PMC
September 2016

Ichthyotoxic Karlodinium veneficum (Ballantine) J Larsen in the Upper Swan River Estuary (Western Australia): Ecological conditions leading to a fish kill.

Harmful Algae 2015 Sep 12;48:83-93. Epub 2015 Aug 12.

University of Maryland Center for Environmental Science, Institute of Marine and Environmental Technology, 701 E. Pratt St., Baltimore, MD 21202, USA.

Ichthyotoxic Karlodinium veneficum has become a persistent problem in the eutrophic Swan River Estuary (SRE) near Perth, Western Australia. Karlotoxin (KmTx) concentrations and K. veneficum were sampled from March to July 2005, spanning a bloom confirmed by microscopy and genetics (ITS sequence), and a fish kill coincident with end of the bloom. The objective of this study was to investigate K. veneficum cell and toxin dynamics, and water quality conditions, leading up to the bloom and fish kill in this estuarine system. Abundance of K. veneficum increased as diatom abundance decreased over a 3-month period (Jan-Mar) preceding the bloom. Low freshwater flow to the SRE characterized the bloom initiation period, while elevated seasonal flows altered water quality and preceded the end of the bloom and fish kill. The bloom of K. veneficum was localized over a bottom layer of hypoxic water in a stratified water column. Low nitrate levels, DIN:DIP (mol) near unity, and particulate C:N:P of K. veneficum-rich water samples were consistent with nitrogen limitation of phytoplankton. A KmTx 2 congener was present in the concentration range 0-1052 ng KmTx mL, levels that were sufficient to kill larval fish in the laboratory within 4 h. A KmTx cell quota of 2.8 pg KmTx cell was estimated for the bloom, which is moderately high for the species. Gill histopathology of fish from this fish kill showed signs of damage similar to those caused by KmTx in the lab. Results from this study suggest that conditions in the SRE, including elevated abundance and KmTx cell quotas, as well as hypoxia in the upper SRE, likely contribute to seasonal fish kills observed in this system.
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http://dx.doi.org/10.1016/j.hal.2015.07.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5026246PMC
September 2015

Employing a socio-ecological systems approach to engage harmful algal bloom stakeholders.

Aquat Ecol 2016 Sep 11;50(3):577-594. Epub 2015 Dec 11.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Sciences, 701 E. Pratt Street, Baltimore, MD 21202, USA.

Harmful algal blooms (HABs) pose substantial health risks to seafood consumers, drinking water supplies, and recreationalists with apparent increases associated with anthropogenic eutrophication of freshwaters and coastal areas. Attempts to intervene in these blooms can be met with reticence by citizens, non-governmental organizations, and officials, often due to local perceptions and beliefs. Hence, the social sciences have an important role to play in HAB research and mitigation. Much of the social science HAB research to date has focused on how best to communicate associated risks and appropriate behavioral responses to affected local communities. The emphasis has been on the direct human impacts, particularly in the areas of health outcomes and identification of any sociocultural and economic barriers to proposed mitigation. While this focus is warranted and valuable, there is also a need to understand HABs as part of a larger human-environmental coupled system, where blooms trigger a wide range of cultural and behavioral responses that are driven by how blooms impact other social and ecosystem dynamics. The research presented here describes a case study of a bloom in a lake in the Chesapeake Bay watershed where anthropologists worked with HAB researchers. The results of this interdisciplinary collaboration show that approaching the bloom and mitigation within a 'socio-ecological systems' framework provides stakeholders with a range of rationales and approaches for addressing HAB mitigation, enhancing both short-term successes and longer-term opportunities, even if is still present in the lake.
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http://dx.doi.org/10.1007/s10452-015-9562-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6777728PMC
September 2016

Stereochemical Studies of the Karlotoxin Class Using NMR Spectroscopy and DP4 Chemical-Shift Analysis: Insights into their Mechanism of Action.

Angew Chem Int Ed Engl 2015 Dec 16;54(52):15705-10. Epub 2015 Nov 16.

Department of Pharmacognosy, Pharmacology, School of Pharmacy, and Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677 (USA).

After publication of karlotoxin 2 (KmTx2; 1), the harmful algal bloom dinoflagellate Karlodinium sp. was collected and scrutinized to identify additional biologically active complex polyketides. The structure of 1 was validated and revised at C49 using computational NMR tools including J-based configurational analysis and chemical-shift calculations. The characterization of two new compounds [KmTx8 (2) and KmTx9 (3)] was achieved through overlaid 2D HSQC NMR techniques, while the relative configurations were determined by comparison to 1 and computational chemical-shift calculations. The detailed evaluation of 2 using the NCI-60 cell lines, NMR binding studies, and an assessment of the literature supports a mode of action (MoA) for targeting cancer-cell membranes, especially of cytostatic tumors. This MoA is uniquely different from that of current agents employed in the control of cancers for which 2 shows sensitivity.
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http://dx.doi.org/10.1002/anie.201507418DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4870721PMC
December 2015

A fish kill associated with a bloom of in a coastal lagoon in Sydney, Australia.

Harmful Algae 2015 Nov 10;49:19-28. Epub 2015 Sep 10.

Warringah Council, Natural Environment Unit, Dee Why NSW, Australia.

We report on a dense bloom (~1.80 × 10 cells mL) of the marine dinoflagellate species (Genotype 2) in a shallow, small intermittently open coastal lagoon in south eastern Australia. This bloom co-occurred with the deaths of >300 individuals of three different species of fish. The opening of the lagoon to the ocean, as well as localized high nutrient levels, preceded the observations of very high cell numbers. is usually benthic and sediment-dwelling, but temporarily became abundant throughout the water column in this shallow (<2 m) sandy habitat. Histopathological results showed that the individuals examined had damage to epithelial and gill epithelial cells. An analysis of the bloom water indicated the presence of a compound with a retention time and UV spectra similar to Luteophanol A, a compound known from a strain of Assays with a fish gill cell line were conducted using a purified compound from cells concentrated from the bloom, and was found to cause a loss of 87% in cell viability in 6 h. The fish deaths were likely due to the low dissolved oxygen levels in the water and/or the presence of Luteophanol A-like compounds released during the bloom.
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http://dx.doi.org/10.1016/j.hal.2015.08.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6738569PMC
November 2015

Interactions between and from the East China Sea.

Harmful Algae 2015 Nov 15;49:50-57. Epub 2015 Sep 15.

Key Laboratory of Applied Marine Biotechnology (Ningbo University), Ministry of Education, Ningbo, China.

The dinoflagellate is a dominant harmful algal bloom (HAB) species on the East China Sea (ECS) coast. The co-occurrence of with is often observed and can later develop into dense blooms. However, the role of in population dynamics is unknown. In the current study, three (GM1, GM2, and GM3) strains were isolated from the ECS with one (GM1) from a mixed, dense bloom of and other HAB species. All three isolates had identical ITS sequences that were concordant with the species designation. Unique karlotoxin congeners were isolated from one strain (GM2). The sterol compositions of and were consistent with sensitivity to karlotoxin in the former and insensitivity in the latter. Additional experimentation showed that: (1)in monocultures, higher growth rate of than is observed in nutrient-enriched and nutrient-depleted media. In co-cultures, the growth of is inhibited; (2) feeding on by is clearly demonstrated by fluorescent dye tracking; and (3) the isolated karlotoxin is lethal to in a concentration-dependent manner. From these studies we propose that may play a negative role in bloom maintenance and that may in turn be a bloom initiator as a prey item for .
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http://dx.doi.org/10.1016/j.hal.2015.08.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6512812PMC
November 2015

Effect of PCB Bioavailability Changes in Sediments on Bioaccumulation in Fish.

Environ Sci Technol 2015 Oct 6;49(20):12405-13. Epub 2015 Oct 6.

Department of Chemical, Biochemical, and Environmental Engineering, University of Maryland Baltimore County , 1000 Hilltop Circle, Baltimore, Maryland 21250, United States.

In situ sediment amendment with sorbents such as activated carbon (AC) can effectively reduce the bioavailability of hydrophobic organic chemicals such as polychlorinated biphenyls (PCBs). However, there is limited experimental or modeling assessment of how bioavailability changes in sediments impact bioaccumulation in fish - the primary risk driver for exposure to humans and top predators in the aquatic ecosystem. In the present study we performed laboratory aquarium experiments and modeling to explore how PCB sorption in sediments impacted exposure pathways and bioaccumulation in fish. Results showed that freely dissolved PCBs in porewater and overlying water measured by passive sampling were reduced by more than 95% upon amendment with 4.5% fine granular AC. The amendment also reduced the PCB uptake in fish by 87% after 90 days of exposure. Measured freely dissolved concentrations were incorporated in equilibrium and kinetic models for predicting uptake by fish. Predicted uptake using the kinetic model was generally within a factor of 2 for total PCBs measured in fish. The kinetic model output was most sensitive to overlying water PCBs, lipid fraction, and dissolved oxygen concentration (regulating gill ventilation). Our results indicate that by incorporating changes in freely dissolved PCB concentrations in bioaccumulation models it is possible to predict effectiveness of sediment remediation in reducing PCB uptake in fish.
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http://dx.doi.org/10.1021/acs.est.5b03107DOI Listing
October 2015

The alveolate translation initiation factor 4E family reveals a custom toolkit for translational control in core dinoflagellates.

BMC Evol Biol 2015 Feb 10;15:14. Epub 2015 Feb 10.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, USA.

Background: Dinoflagellates are eukaryotes with unusual cell biology and appear to rely on translational rather than transcriptional control of gene expression. The eukaryotic translation initiation factor 4E (eIF4E) plays an important role in regulating gene expression because eIF4E binding to the mRNA cap is a control point for translation. eIF4E is part of an extended, eukaryote-specific family with different members having specific functions, based on studies of model organisms. Dinoflagellate eIF4E diversity could provide a mechanism for dinoflagellates to regulate gene expression in a post-transcriptional manner. Accordingly, eIF4E family members from eleven core dinoflagellate transcriptomes were surveyed to determine the diversity and phylogeny of the eIF4E family in dinoflagellates and related lineages including apicomplexans, ciliates and heterokonts.

Results: The survey uncovered eight to fifteen (on average eleven) different eIF4E family members in each core dinoflagellate species. The eIF4E family members from heterokonts and dinoflagellates segregated into three clades, suggesting at least three eIF4E cognates were present in their common ancestor. However, these three clades are distinct from the three previously described eIF4E classes, reflecting diverse approaches to a central eukaryotic function. Heterokonts contain four clades, ciliates two and apicomplexans only a single recognizable eIF4E clade. In the core dinoflagellates, the three clades were further divided into nine sub-clades based on the phylogenetic analysis and species representation. Six of the sub-clades included at least one member from all eleven core dinoflagellate species, suggesting duplication in their shared ancestor. Conservation within sub-clades varied, suggesting different selection pressures.

Conclusions: Phylogenetic analysis of eIF4E in core dinoflagellates revealed complex layering of duplication and conservation when compared to other eukaryotes. Our results suggest that the diverse eIF4E family in core dinoflagellates may provide a toolkit to enable selective translation as a strategy for controlling gene expression in these enigmatic eukaryotes.
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http://dx.doi.org/10.1186/s12862-015-0301-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4330643PMC
February 2015

Translating the message: possesses an expanded toolkit of protein translation initiation factors.

Mar Freshw Harmful Algae (2014) 2015 ;2014:237-240

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Sciences; 701 East Pratt Street, Baltimore, MD USA 21202.

Dinoflagellates are unusual eukaryotes with large genomes and a reduced role for transcriptional regulation compared to other eukaryotes. The mRNA in dinoflagellates is -spliced with a 5'-spliced-leader sequence, yielding a 22-nucleotide 5'-sequence with a methylated nucleotide cap. Since the control of gene expression is primarily post-transcriptional, this study focuses on mRNA recruitment as a means for regulating gene expression and specifically on the diversity of eIF4E family members. Three novel clades related to the cap binding initiation factor eIF4E have been recognized in alveolates that are distinct from the three metazoan classes of eIF4E. We have analyzed the characteristics of five of the fourteen eIF4E family members from , four from clade 1 and one from clade 2. Members of each clade all bear the distinctive features of a cap-binding protein. We examined their ability to interact with the cap analogue, mGTP using an bead-binding assay. We show that recombinant eIF4E-1 family members are able to bind the cap analogue mGTP, but eIF4E-2b binds poorly. Overall, the eIF4E-1 family members may be serving as general cap-binding translation initiation factors, while the eIF4E-2 (and perhaps eIF4E-3) family members may serve a regulatory role in gene expression.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6755914PMC
January 2015

The cytotoxic mechanism of karlotoxin 2 (KmTx 2) from Karlodinium veneficum (Dinophyceae).

Aquat Toxicol 2015 Feb 15;159:148-55. Epub 2014 Dec 15.

University of Maryland, Baltimore, Center for Biomedical Engineering and Technology and Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.

This study demonstrates that the polyketide toxin karlotoxin 2 (KmTx 2) produced by Karlodinium veneficum, a dinoflagellate associated with fish kills in temperate estuaries world-wide, alters vertebrate cell membrane permeability. Microfluorimetric and electrophysiological measurements were used to determine that vertebrate cellular toxicity occurs through non-selective permeabilization of plasma membranes, leading to osmotic cell lysis. Previous studies showed that KmTx 2 is lethal to fish at naturally-occurring concentrations measured during fish kills, while sub-lethal doses severely damage gill epithelia. This study provides a mechanistic explanation for the association between K. veneficum blooms and fish kills that has long been observed in temperate estuaries worldwide.
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http://dx.doi.org/10.1016/j.aquatox.2014.11.028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4343303PMC
February 2015

Acute toxicity of karlotoxins to mice.

Toxicon 2014 Nov 20;90:184-90. Epub 2014 Aug 20.

Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.

Karlotoxins, polyketide derivatives produced by the dinoflagellate Karlodinium veneficum, are associated with fish kills in temperate estuaries world-wide. In this study, the acute effects of 3 pure karlotoxin analogs (KmTx 1, KmTx 3 and KmTx 2) have been examined in mice. Transient lethargy and increased respiratory rates were observed soon after dosing with the karlotoxins by intraperitoneal injection, but no deaths were recorded in animals dosed with KmTx 2 at up to 500 μg/kg or with KmTx 1 or KmTx 3 at up to 4000 μg/kg. Animals dosed intraperitoneally with KmTx 1 and KmTx 3 at 4000 μg/kg showed a pronounced decrease in food and water intake, lasting 3-4 days after dosing, accompanied by a significant decrease in body weight. After this time, the lost body weight was regained and the behavior and appearance of the mice remained normal throughout the following 10-day observation period. No effects were seen in mice dosed orally with KmTx 1 or KmTx 3 at a dose of 4000 μg/kg. It is concluded that contamination of seafood if it were to occur with these karlotoxins is unlikely to pose a major risk of acute intoxication in consumers.
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http://dx.doi.org/10.1016/j.toxicon.2014.08.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4498405PMC
November 2014

Biological sunscreens tune polychromatic ultraviolet vision in mantis shrimp.

Curr Biol 2014 Jul 3;24(14):1636-1642. Epub 2014 Jul 3.

Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.

Video Abstract: Stomatopod crustaceans, or mantis shrimp, are renowned for their complex visual systems. Their array of 16 types of photoreceptors provides complex color reception, as well as linear and circular polarization sensitivity [1-6]. The least-understood components of their retina are the UV receptors, of which there are up to six distinct, narrowly tuned spectral types [4]. Here we show that in the stomatopod species Neogonodactylus oerstedii, this set of receptors is based on only two visual pigments. Surprisingly, five of the six UV receptor types contain the same visual pigment. The various UV receptors are spectrally tuned by a novel set of four short- and long-pass UV-specific optical filters in the overlying crystalline cones. These filters are composed of various mycosporine-like amino acid (MAA) pigments. Commonly referred to as "nature's sunscreens," MAAs are usually employed for UV photoprotection [7, 8], but mantis shrimp uniquely incorporate them into powerful spectral tuning filters, extending and diversifying their preeminently elaborate photoreceptive arsenal.
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http://dx.doi.org/10.1016/j.cub.2014.05.071DOI Listing
July 2014

Taurine supplementation of plant derived protein and n-3 fatty acids are critical for optimal growth and development of cobia, Rachycentron canadum.

Lipids 2013 Sep 25;48(9):899-913. Epub 2013 Jul 25.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, 701 East Pratt St., Baltimore, MD 21202, USA.

We examined growth performance and the lipid content in juvenile cobia, Rachycentron canadum, fed a taurine supplemented (1.5 %), plant protein based diet with two fish oil replacements. The first fish oil replacement was a thraustochytrid meal (TM + SOY) plus soybean oil (~9 % CL) and the second was a canola oil supplemented with the essential fatty acids (EFA) docosahexaenoic acid (DHA) and arachidonic acid (ARA) (~8 % CL). The diet using the thraustochytrid meal plus soybean oil performed equivalently to the fish oil diet; both resulting in significantly higher growth rates, lower feed conversion ratios, and higher survival than the supplemented canola oil diet, even though all three diets were similar in overall energy and met known protein and lipid requirements for cobia. The poor performance of the canola oil diet was attributed to insufficient addition of EFA in the supplemented canola oil source. Increasing levels of EFA in the supplemented canola oil above 0.5 g EFA kg(-1) would likely improve results with cobia. When fish fed either of the fish oil replacement diets were switched to the fish oil control diet, fatty acid profiles of the fillets were observed to transition toward that of the fish oil diet and could be predicted based on a standard dilution model. Based on these findings, a formulated diet for cobia can be produced without fish products providing 100 % survivorship, specific growth rates greater than 2.45 and feed conversion ratios less than 1.5, as long as taurine is added and EFA levels are above 0.5 g EFA kg(-1).
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http://dx.doi.org/10.1007/s11745-013-3814-2DOI Listing
September 2013

Responses of Nannochloropsis oceanica IMET1 to Long-Term Nitrogen Starvation and Recovery.

Plant Physiol 2013 Jun 1;162(2):1110-26. Epub 2013 May 1.

Research Center for Harmful Algae and Marine Biology, Jinan University, Guangzhou 510632, China.

The Nannochloropsis genus contains oleaginous microalgae that have served as model systems for developing renewable biodiesel. Recent genomic and transcriptomic studies on Nannochloropsis species have provided insights into the regulation of lipid production in response to nitrogen stress. Previous studies have focused on the responses of Nannochloropsis species to short-term nitrogen stress, but the effect of long-term nitrogen deprivation remains largely unknown. In this study, physiological and proteomic approaches were combined to understand the mechanisms by which Nannochloropsis oceanica IMET1 is able to endure long-term nitrate deprivation and its ability to recover homeostasis when nitrogen is amended. Changes of the proteome during chronic nitrogen starvation espoused the physiological changes observed, and there was a general trend toward recycling nitrogen and storage of lipids. This was evidenced by a global down-regulation of protein expression, a retained expression of proteins involved in glycolysis and the synthesis of fatty acids, as well as an up-regulation of enzymes used in nitrogen scavenging and protein turnover. Also, lipid accumulation and autophagy of plastids may play a key role in maintaining cell vitality. Following the addition of nitrogen, there were proteomic changes and metabolic changes observed within 24 h, which resulted in a return of the culture to steady state within 4 d. These results demonstrate the ability of N. oceanica IMET1 to recover from long periods of nitrate deprivation without apparent detriment to the culture and provide proteomic markers for genetic modification.
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http://dx.doi.org/10.1104/pp.113.214320DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3668043PMC
June 2013