Special Issue "Toxins from Aquatic Organisms"

Guest Editor
Prof. Dr. David Sheehan
Proteomic Research Laboratory, Department of Biochemistry, University College Cork, Lee Maltings Prospect Row, Mardyke, Cork, Ireland
Website: http://www.ucc.ie/ucc/depts/biochemistry/staff/dsheehan.html
E-Mail:
Interests: enzymology and evolution of glutathione transferases; application of proteomics to study of oxidative stress; implications of reactive oxygen and nitrogen species for kidney function; environmental toxicology; nanomaterials as emerging toxicological threats

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.org 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.

• toxin
• freshwater
• marine
• dinoflagellates
• cyanobacteria
• pollution
• red tide
• algal bloom
• global warming

Type of Paper: Article
Title: Modulation of Some Hemato-Immunological Parameters of Different Bivalves During a Dinoflagellate (Dinophysis Acuminata) Natural Bloom in Santa Catarina Island, Brazil
Authors: Danielle F. Mello, Luis A. O. Proença and Margherita A. Barracco
Affiliation: Laboratório de Imunologia Aplicada à Aquicultura, Departamento de Biologia Celular Embriologia e Genética, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brasil; E-Mail: barracco@mbox1.ufsc.br (M.A.B.)
Abstract: Outbreaks of harmful algae blooms (HABs) are becoming more and more frequent in the Brazilian coast and are seriously threatening mollusk cultivations. Most of the current studies are directed to the effect of algal toxins on mollusk consumers but their effect on mollusk themselves is poorly known. The aim of this study was to examine the effect of a bloom of D. acuminata on the immune system of three bivalve species: the oyster Crassostrea gigas, the mussel Perna perna and the clam Anomalocardia brasiliana. All animals were obtained from a cultivation farm located at the southern bay of Santa Catarina island during a D. acuminata outbreak (17,600 cells/L). After the outbreak, the animals were sampled again (controls). A number of hemato-immunological parameters were determined from bivalve hemolymph: total (THC) and differential (DHC) hemocyte counts, percentage of apoptotic hemocytes (AH), protein concentration (PC), hemagglutinating titer (HT) and phenoloxidase (PO) activity. The results showed that during the HAB, the levels of some parameters were altered in some bivalve species. There was a significant increase on THC and PC in mussels and clams but not in oysters. On the other hand, the percentage of granulocytes decreased significantly and PO activity augmented strongly only in mussels. The HT and the percentage of AH did not vary in any bivalve species. These results suggested that P. perna was the most susceptible bivalve species to D. acuminata bloom and C. gigas the least immunosensitive.

Type of Paper: Review
Title: α-Conotoxins and Their Synthetic Analogues as Probes for Studying Nicotinic Acetylcholine Receptors and in the Development of Novel Drugs
Author: Christopher J. Armishaw
Affiliation: Torrey Pines Institute for Molecular Studies, 11350 SW Village Pkwy, Port St Lucie, FL 34987, USA; E-Mail: carmishaw@tpims.org
Abstract: 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 have aided in the design of synthetic analogues with improved pharmacological properties. This review examines 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.

Type of Paper: Review
Title: Diversity and Impact of Prokaryotic Toxins on Aquatic Environments: A Review
Authors: Elisabete Valério¹, Sandra Chaves ² and Rogério Tenreiro ²
Affiliations: ¹ Centro de Recursos Microbiológicos (CREM), Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal
² Centro de Biodiversidade, Genómica Integrativa e Funcional (BioFIG), Faculdade de Ciências, Universidade de Lisboa, Edificio ICAT, Campus da FCUL, Campo Grande, 1740-016, Lisboa, Portugal; E-Mail: rptenreiro@fc.ul.pt (R.T.)
Abstract: Microorganisms are ubiquitous in all habitats and are recognized by their metabolic versatility and ability to produce many bioactive compounds including hydrolytic enzymes, antibiotics, antitumorals and 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 toxins responsible for allergenic reactions (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. This particular type of peptide synthesis allows the arrangement of molecular structures not possible to be obtained by ribosomal synthesis. 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, V. parahaemolyticus and V. vulnificus pathogenesis, but there are evidences for the existence of other potential toxins. Similarly, several Clostridium species can produce potent neurotoxins. Although there are not considered aquatic microorganisms, they are ubiquitous in 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 for their hazard grade. Campylobacter spp. and Escherichia coli are also water contaminants and are able to produce important toxins after infecting their hosts (e.g. Shiga toxin of E. coli). Other bacteria associated with aquatic environments are emerging as toxin producers. Pseudomonas species, namely P. aeruginosa, Legionella pneumophila, Mycobacterium spp. and Aeromonas hydrophila have also been described as responsible for the synthesis of several exotoxins, enterotoxins and citotoxins.
This review presents an overview about the diversity of toxins produced by prokaryotic microorganisms associated with aquatic habitats and their impact on environment and life and health of humans and other animals. Moreover, important issues like the availability of these toxins in the environment, contamination sources and pathways and genes involved in their biosynthesis are also discussed.
Keywords: diversity of toxins; impact of toxins; prokaryotes; aquatic