http://www.mdpi.com/journal/toxins/special_issues/toxins-aquat-org/ Dear Colleagues, Many toxins are produced in aquatic organisms ranging from cyanobacteria, to dinoflagellates, algae and other organisms both of freshwater and marine origin. As natural compounds, these toxins have not been thought of as environmental pollutants but they do pose toxic threats to other aquatic life-forms and to human health and they can be bioaccumulated and biotransformed in target organisms resulting in a more complicated toxic threat. This is exemplified by the paralytic shellfish poisoning of humans on eating shellfish contaminated by dinoflagellate toxins arising from algal “blooms”. Such blooms are occurring more often and more severely worldwide with serious implications for aquaculture, mariculture, environmental and human health. This special issue deals with structure, analysis, potential as novel drugs, toxic effects, biotransformation/accumulation and detoxification and environmental implications of toxins from aquatic organisms. Prof. David Sheehan Guest Editor Submission All manuscripts should be submitted to toxins@mdpi.com with a copy to the Guest Editor. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website. Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxins is an international peer-reviewed Open Access monthly journal published by MDPI.   Please visit the Instructions for Authors page before submitting a manuscript. Article Processing Charges (APC) for publication in this Open Access journal will be waived for well-prepared manuscripts submitted before 30 June 2010. English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections. http://www.mdpi.com/2072-6651/2/10/2359/ Microorganisms are ubiquitous in all habitats and are recognized by their metabolic versatility and ability to produce many bioactive compounds, including toxins. Some of the most common toxins present in water are produced by several cyanobacterial species. As a result, their blooms create major threats to animal and human health, tourism, recreation and aquaculture. Quite a few cyanobacterial toxins have been described, including hepatotoxins, neurotoxins, cytotoxins and dermatotoxins. These toxins are secondary metabolites, presenting a vast diversity of structures and variants. Most of cyanobacterial secondary metabolites are peptides or have peptidic substructures and are assumed to be synthesized by non-ribosomal peptide synthesis (NRPS), involving peptide synthetases, or NRPS/PKS, involving peptide synthetases and polyketide synthases hybrid pathways. Besides cyanobacteria, other bacteria associated with aquatic environments are recognized as significant toxin producers, representing important issues in food safety, public health, and human and animal well being. Vibrio species are one of the most representative groups of aquatic toxin producers, commonly associated with seafood-born infections. Some enterotoxins and hemolysins have been identified as fundamental for V. cholerae and V. vulnificus pathogenesis, but there is evidence for the existence of other potential toxins. Campylobacter spp. and Escherichia coli are also water contaminants and are able to produce important toxins after infecting their hosts. Other bacteria associated with aquatic environments are emerging as toxin producers, namely Legionella pneumophila and Aeromonas hydrophila, described as responsible for the synthesis of several exotoxins, enterotoxins and cytotoxins. Furthermore, several Clostridium species can produce potent neurotoxins. Although not considered aquatic microorganisms, they are ubiquitous in the environment and can easily contaminate drinking and irrigation water. Clostridium members are also spore-forming bacteria and can persist in hostile environmental conditions for long periods of time, contributing to their hazard grade. Similarly, Pseudomonas species are widespread in the environment. Since P. aeruginosa is an emergent opportunistic pathogen, its toxins may represent new hazards for humans and animals. This review presents an overview of the diversity of toxins produced by prokaryotic microorganisms associated with aquatic habitats and their impact on environment, life and health of humans and other animals. Moreover, important issues like the availability of these toxins in the environment, contamination sources and pathways, genes involved in their biosynthesis and molecular mechanisms of some representative toxins are also discussed. http://www.mdpi.com/2072-6651/2/10/2359/ Mon, 18 Oct 2010 00:00:00 CEST Toxins 2010-10-18 2 10 Review 2359 2410 2072-6651 Diversity and Impact of Prokaryotic Toxins on Aquatic Environments: A Review 2010-10-18 doi: 10.3390/toxins2102359 Elisabete Valério Sandra Chaves Rogério Tenreiro http://www.mdpi.com/2072-6651/2/6/1471/ α-Conotoxins are peptide neurotoxins isolated from venomous marine cone snails that are potent and selective antagonists for different subtypes of nicotinic acetylcholine receptors (nAChRs). As such, they are valuable probes for dissecting the role that nAChRs play in nervous system function. In recent years, extensive insight into the binding mechanisms of α-conotoxins with nAChRs at the molecular level has aided in the design of synthetic analogs with improved pharmacological properties. This review examines the structure-activity relationship studies involving α-conotoxins as research tools for studying nAChRs in the central and peripheral nervous systems and their use towards the development of novel therapeutics. http://www.mdpi.com/2072-6651/2/6/1471/ Mon, 14 Jun 2010 00:00:00 CEST Toxins 2010-06-14 2 6 Review 1471 1499 2072-6651 Synthetic α-Conotoxin Mutants as Probes for Studying Nicotinic Acetylcholine Receptors and in the Development of Novel Drug Leads 2010-06-14 doi: 10.3390/toxins2061471 Armishaw http://www.mdpi.com/2072-6651/2/5/1166/ This study aimed to verify if Dinophysis acuminata natural blooms affected the immune system of three bivalves: the oyster, Crassostrea gigas, the mussel, Perna perna, and the clam, Anomalocardia brasiliana. Animals were obtained from a renowned mariculture farm in the southern bay of Santa Catarina Island during, and 30 days after (controls), an algal bloom. Various immunological parameters were assessed in the hemolymph of the animals: total and differential hemocyte counts, percentage of apoptotic hemocytes, protein concentration, hemagglutinating titer and phenoloxidase activity. The results showed that the mussel was the most affected species, with several altered immune parameters, whereas the immunological profile of clams and oysters was partially and completely unaffected, respectively. http://www.mdpi.com/2072-6651/2/5/1166/ Tue, 25 May 2010 00:00:00 CEST Toxins 2010-05-25 2 5 Article 1166 1178 2072-6651 Comparative Study of Various Immune Parameters in Three Bivalve Species during a Natural Bloom of Dinophysis acuminata in Santa Catarina Island, Brazil 2010-05-25 doi: 10.3390/toxins2051166 Mello Proença Barracco http://www.mdpi.com/2072-6651/2/4/905/ Photobacterium damselae subsp. piscicida (Phdp) is a Gram-negative pathogen agent of an important fish septicemia. The key virulence factor of Phdp is the plasmid-encoded exotoxin AIP56, which is secreted by exponentially growing pathogenic strains. AIP56 has 520 amino acids including an N-terminal cleavable signal peptide of 23 amino acid residues, two cysteine residues and a zinc-binding region signature HEXXH that is typical of most zinc metallopeptidases. AIP56 induces in vitro and in vivo selective apoptosis of fish macrophages and neutrophils through a caspase-3 dependent mechanism that also involves caspase-8 and -9. In vivo, the AIP56-induced phagocyte apoptosis progresses to secondary necrosis with release of cytotoxic phagocyte molecules including neutrophil elastase. Fish injected with recombinant AIP56 die with a pathology similar to that seen in the natural infection. http://www.mdpi.com/2072-6651/2/4/905/ Mon, 26 Apr 2010 00:00:00 CEST Toxins 2010-04-26 2 4 Review 905 918 2072-6651 AIP56: A Novel Bacterial Apoptogenic Toxin 2010-04-26 doi: 10.3390/toxins2040905 Silva Dos Santos Do Vale http://www.mdpi.com/2072-6651/2/4/878/ 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. http://www.mdpi.com/2072-6651/2/4/878/ Fri, 23 Apr 2010 00:00:00 CEST Toxins 2010-04-23 2 4 Review 878 904 2072-6651 Marine Toxins: Chemistry, Toxicity, Occurrence and Detection, with Special Reference to the Dutch Situation 2010-04-23 doi: 10.3390/toxins2040878 Gerssen Pol-Hofstad Poelman Mulder Van den Top De Boer