YESSOTOXINS—POLYCYCLIC ETHERS FROM DINOFLAGELLATES: RELATIONSHIPS TO DIARRHETIC SHELLFISH TOXINS

Bacterial cellulose loaded with silver nanoparticles as a flexible, stable and sensitive SERS-active substrate for detection of the shellfish toxin DTX-1

Diarrheal shellfish toxins are considered one of the most lethal red tide algae toxins in the worldwide. In this work, we propose an Ag NPs-loaded bacterial cellulose membrane (BCM) surface-enhanced Raman scattering (SERS) sensor based on an aptamer (Apt) for the ultrasensitive detection of dinophysistoxin (DTX-1), a type of diarrheal shellfish toxin. During drying, Ag NPs can be further densified on "gel-like" BCM to form high-density SERS "hot spots". We developed the "Apt-SH@Ag NPs@BCM" SERS sensor and used the competition of DTX-1 and complementary base (Cob) in the process of base complementary pairing to achieve SERS detection of DTX-1, with a minimum detection limit of 9.5 × 10^-10 mol/L. Sample assays showed DTX-1 recovery rates ranging from 95.8% and 108.2% and the detection results were comparable to those obtained by LC-MS. Therefore, this work holds great potential for detecting of toxic substances in shellfish products, especially for the oyster (portuguese oyster) and mussel (blue mussel).

Repeated oral co-exposure to yessotoxin and okadaic acid: a short term toxicity study in mice

The polyethers yessotoxin (YTX) and okadaic acid (OA) are two marine algal toxins frequently associated as edible shellfish contaminants. Seafood contamination by these compounds, also at low concentrations and for a long period of time, can increase the possibility of their simultaneous and repeated ingestion, with possible synergistic toxic effects. Thus, in vivo toxicity by repeated oral exposure to a combination of fixed doses of YTX and OA (1 mg YTX/kg and 0.185 mg OA/kg, daily for 7 days) was investigated in mice, in comparison to that of each toxin alone. No mortality, signs of toxicity, diarrhea or hematological changes was induced by the toxins co-administration or by the single toxins. Light microscopy revealed changes at gastric level (multifocal subacute inflammation, erosions and epithelial hyperplasia) in 2/5 mice co-administered with the toxins. In animals dosed only with OA, epithelial hyperplasia of forestomach and slight focal subacute inflammation of its submucosa were noted. No changes were induced by the treatment with YTX. Ultrastructural analysis of the heart revealed some cardiomyocytes with "loose packing" of myofibrils and aggregated rounded mitochondria in mice co-administered with the toxins or with YTX; OA-treated mice showed only occasional mitochondrial assemblage and dilated sarcomeres. Thus, the combined oral doses of YTX (1 mg/kg/day) and OA (0.185 mg/kg/day) did not exert cumulative or additive toxic effects in mice, in comparison to the single toxins.

Marine toxins: chemistry, toxicity, occurrence and detection, with special reference to the Dutch situation

Various species of algae can produce marine toxins under certain circumstances. These toxins can then accumulate in shellfish such as mussels, oysters and scallops. When these contaminated shellfish species are consumed severe intoxication can occur. The different types of syndromes that can occur after consumption of contaminated shellfish, the corresponding toxins and relevant legislation are discussed in this review. Amnesic Shellfish Poisoning (ASP), Paralytic Shellfish Poisoning (PSP), Diarrheic Shellfish Poisoning (DSP) and Azaspiracid Shellfish Poisoning (AZP) occur worldwide, Neurologic Shellfish Poisoning (NSP) is mainly limited to the USA and New Zealand while the toxins causing DSP and AZP occur most frequently in Europe. The latter two toxin groups are fat-soluble and can therefore also be classified as lipophilic marine toxins. A detailed overview of the official analytical methods used in the EU (mouse or rat bioassay) and the recently developed alternative methods for the lipophilic marine toxins is given. These alternative methods are based on functional assays, biochemical assays and chemical methods. From the literature it is clear that chemical methods offer the best potential to replace the animal tests that are still legislated worldwide. Finally, an overview is given of the situation of marine toxins in The Netherlands. The rat bioassay has been used for monitoring DSP and AZP toxins in The Netherlands since the 1970s. Nowadays, a combination of a chemical method and the rat bioassay is often used. In The Netherlands toxic events are mainly caused by DSP toxins, which have been found in Dutch shellfish for the first time in 1961, and have reoccurred at irregular intervals and in varying concentrations. From this review it is clear that considerable effort is being undertaken by various research groups to phase out the animal tests that are still used for the official routine monitoring programs.

Biosynthesis and molecular genetics of polyketides in marine dinoflagellates

Marine dinoflagellates are the single most important group of algae that produce toxins, which have a global impact on human activities. The toxins are chemically diverse, and include macrolides, cyclic polyethers, spirolides and purine alkaloids. Whereas there is a multitude of studies describing the pharmacology of these toxins, there is limited or no knowledge regarding the biochemistry and molecular genetics involved in their biosynthesis. Recently, however, exciting advances have been made. Expressed sequence tag sequencing studies have revealed important insights into the transcriptomes of dinoflagellates, whereas other studies have implicated polyketide synthase genes in the biosynthesis of cyclic polyether toxins, and the molecular genetic basis for the biosynthesis of paralytic shellfish toxins has been elucidated in cyanobacteria. This review summarises the recent progress that has been made regarding the unusual genomes of dinoflagellates, the biosynthesis and molecular genetics of dinoflagellate toxins. In addition, the evolution of these metabolic pathways will be discussed, and an outlook for future research and possible applications is provided.

Antibody-based sensors: principles, problems and potential for detection of pathogens and associated toxins

Antibody-based sensors permit the rapid and sensitive analysis of a range of pathogens and associated toxins. A critical assessment of the implementation of such formats is provided, with reference to their principles, problems and potential for 'on-site' analysis. Particular emphasis is placed on the detection of foodborne bacterial pathogens, such as Escherichia coli and Listeria monocytogenes, and additional examples relating to the monitoring of fungal pathogens, viruses, mycotoxins, marine toxins and parasites are also provided.

First evidence of okadaic acid in Mytilus galloprovincialis mussels, collected in a Mediterranean Lagoon, Tunisia

Evidence of the presence of okadaic acid (OA) and its monthly fluctuations are reported for the first time in Mytilus galloprovincialis samples collected from June 2005 to May 2006 in the Bizerte Lagoon. All of the samples with the exception of those taken in August 2005 were found to be contaminated. The level of OA in mussels exceeded the regulatory limit of DSP toxins (16 microg OA/100 g mussel meat) within the European Union (2002) in only two cases: in January and February, 2006 with 31.85 +/- 3.06, and 18.86 +/- 1.88 microg OA/100 g mussel meat respectively. During the investigative period, potentially toxic dinoflagellates were observed. The results reported here, although based on limited sampling, demonstrate for the first time the existence of a risk to public health from diarrheic shellfish poisoning in cultivated bivalve mollusc in Tunisia.

Marine toxins: an overview

Oceans provide enormous and diverse space for marine life. Invertebrates are conspicuous inhabitants in certain zones such as the intertidal; many are soft-bodied, relatively immobile and lack obvious physical defenses. These animals frequently have evolved chemical defenses against predators and overgrowth by fouling organisms. Marine animals may accumulate and use a variety of toxins from prey organisms and from symbiotic microorganisms for their own purposes. Thus, toxic animals are particularly abundant in the oceans. The toxins vary from small molecules to high molecular weight proteins and display unique chemical and biological features of scientific interest. Many of these substances can serve as useful research tools or molecular models for the design of new drugs and pesticides. This chapter provides an initial survey of these toxins and their salient properties.

Marine natural products

This review covers the literature published in 2006 for marine natural products, with 758 citations (534 for the period January to December 2006) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, cnidaria, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (779 for 2006), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Biotechnological significance of toxic marine dinoflagellates

Dinoflagellates are microalgae that are associated with the production of many marine toxins. These toxins poison fish, other wildlife and humans. Dinoflagellate-associated human poisonings include paralytic shellfish poisoning, diarrhetic shellfish poisoning, neurotoxic shellfish poisoning, and ciguatera fish poisoning. Dinoflagellate toxins and bioactives are of increasing interest because of their commercial impact, influence on safety of seafood, and potential medical and other applications. This review discusses biotechnological methods of identifying toxic dinoflagellates and detecting their toxins. Potential applications of the toxins are discussed. A lack of sufficient quantities of toxins for investigational purposes remains a significant limitation. Producing quantities of dinoflagellate bioactives requires an ability to mass culture them. Considerations relating to bioreactor culture of generally fragile and slow-growing dinoflagellates are discussed. Production and processing of dinoflagellates to extract bioactives, require attention to biosafety considerations as outlined in this review.