A Review on the Biodiversity and Biogeography of Toxigenic Benthic Marine Dinoflagellates of the Coasts of Latin America

Many benthic dinoflagellates are known or suspected producers of lipophilic polyether phycotoxins, particularly in tropical and subtropical coastal zones. These toxins are responsible for diverse intoxication events of marine fauna and human consumers of seafood, but most notably in humans, they cause toxin syndromes known as diarrhetic shellfish poisoning (DSP) and ciguatera fish poisoning (CFP). This has led to enhanced, but still insufficient, efforts to describe benthic dinoflagellate taxa using morphological and molecular approaches. For example, recently published information on epibenthic dinoflagellates from Mexican coastal waters includes about 45 species from 15 genera, but many have only been tentatively identified to the species level, with fewer still confirmed by molecular criteria. This review on the biodiversity and biogeography of known or putatively toxigenic benthic species in Latin America, restricts the geographical scope to the neritic zones of the North and South American continents, including adjacent islands and coral reefs. The focus is on species from subtropical and tropical waters, primarily within the genera Prorocentrum, Gambierdiscus/Fukuyoa, Coolia, Ostreopsis and Amphidinium. The state of knowledge on reported taxa in these waters is inadequate and time-series data are generally lacking for the prediction of regime shift and global change effects. Details of their respective toxigenicity and toxin composition have only recently been explored in a few locations. Nevertheless, by describing the specific ecosystem habitats for toxigenic benthic dinoflagellates, and by comparing those among the three key regions - the Gulf of Mexico, Caribbean Sea and the subtropical and tropical Pacific coast, insights for further risk assessment of the global spreading of toxic benthic species is generated for the management of their effects in Latin America

Toxinas paralizantes tipo benzoil en el dinoflagelado Gymnodinium catenatum Graham y modelo teórico de interacción con el canal de sodio.

Resumen En este estudio se analizaron extractos de G. catenatum para estudiar la composición y variación de sus toxinas, incluyendo los análogos tipo benzoil, por diferentes técnicas cromatográficas y espectroscópicas, como LC-FLD, HILIC-MS/MS, 1H RMN y espectroscopia UV. También se sometió a la molécula de saxitoxina y 34 análogos a estudios de docking sobre el modelo del canal de sodio regulado por voltaje Nav 1.4 para conocer las interacciones sobre su molécula blanco. Los resultados obtenidos mostraron la presencia de estas toxinas en los cinco aislados analizados y durante todas las etapas de cultivo, lo que indica que se producen de manera constante. Se observaron variaciones en todas las toxinas relacionadas con el medio de cultivo y el aislado, y las toxinas tipo benzoil no fueron una excepción. Se encontraron diferencias biológicas y en el perfil de toxinas entre aislados, debidas a la variabilidad intraespecífica. Las toxinas paralizantes exhiben diferentes modos de unión con energías similares en el canal de sodio regulado por voltaje, y las toxinas tipo benzoil exhiben una toxicidad teórica digna de estudiar más a fondo. La simulación in silico llevada a cabo en este estudio es la primera con estas toxinas, y provee una acercamiento hacia un mejor entendimiento del modo de acción de la saxitoxina y sus análogos. Los análogos tipo benzoil han sido poco estudiados y el reporte de su existencia en aislados mexicanos es de gran importancia porque podrían representar un riesgo para la salud pública, pero también su conocimiento genera la oportunidad de continuar su investigación, una tarea necesaria en un futuro muy próximo. ABSTRACT In this study, we analyzed Gymnodinium catenatum extracts to investigate their toxin composition, including the benzoyl analogs, by different chromatographic and spectroscopic techniques, such as LC-FLD, HILIC-MS/MS, 1H NMR, and UV spectroscopy. We also submitted STX and 34 analogs to a docking study on the tri-dimensional channel Nav 1.4. The results showed media and isolate related variations in all toxins, and benzoyl toxins were not an exception. We were capable to demonstrate the presence of these toxins in all the analyzed isolates and during all culture stages, and found many biological and toxin profile differences between isolates due to intraspecific variability. We demonstrate that these toxins exhibit different binding modes with similar free binding energies, and that these alternative binding modes are equally probable. Our simulation constitutes the first in silico modeling study on benzoyl-type paralytic toxins and provides an approach towards a better understanding of the mode of action of STX and its analogs. We propose that the principal binding that governs ligand recognition is mediated by electrostatic interactions. Benzoyl analogs have been poorly studied and the report on their existence in Mexican isolates is of great importance because they could represent a public health risk, but in the other hand, their existence generates the opportunity to continue its research, a necessary task in the future

Toxicity Bioassay and Cytotoxic Effects of the Benthic Marine Dinoflagellate Amphidinium operculatum

Benthic dinoflagellates produce a wide array of bioactive compounds, primarily polyketides, that cause toxic effects on human consumers of seafood and perhaps mediate species interactions in the benthic microenvironment. This study assesses toxic and other bioactive effects of the benthic dinoflagellate Amphidinium operculatum (strain AA60) in two targeted bioassays. The brine shrimp (Artemia salina) bioassay revealed lethal effects of direct exposure to live dinoflagellate cells (Treatment A) and even higher potency with ethanolic extracts of lysed cells (Treatment D). There were no inimical bioactive effects of components released to the aqueous growth medium (Treatment B) or from aqueous cell lysates (Treatment C). The hypothesis that released bioactive compounds provide a chemical defense against metazoan grazers is therefore not supported by these results. The cytotoxic effect of ethanolic crude extracts of this dinoflagellate exhibited mild to high growth reduction effects on six human cancer cell lines. In particular, crude cell-free extracts proved highly growth-inhibitory activity towards breast and lung cancer cell lines MCF-7 and SKLU-1, respectively. Preliminary anti-cancer results indicate that natural bioactive compounds from Amphidinium are worthy of structural characterization and further toxicological investigation as potential therapeutants

Diversity of Bacterioplankton and Bacteriobenthos from the Veracruz Reef System, Southwestern Gulf of Mexico

Bacterial diversity was explored among field samples and cultured isolates from coral reefs within the Veracruz Reef System. Bacterioplankton and bacteriobenthos were characterized by pyrosequencing 16S rRNA genes. Identified sequences belonged to the kingdom Bacteria and classified into 33 phyla. Proteobacteria (likely SAR11 clade) dominated in collective field samples, whereas Firmicutes were the most abundant taxa among cultured isolates. Bioinformatic sorting of sequences to family level revealed 223 bacterial families. Pseudomonadaceae, Exiguobacteraceae and Bacillaceae were dominant among cultured isolates. Vibrionaceae, Alteromonadaceae, and Flavobacteriaceae dominated in reef-associated sediments, whereas Rickettsiaceae and Synechoccaceae were more highly represented in the water column. Bacterial communities from sediments were more diverse than from the water column. This study reveals cryptic bacterial diversity among microenvironmental components of marine microbial reef communities subject to differential influence of anthropogenic stressors. Such investigations are critical for constructing scenarios of environmentally induced shifts in bacterial biodiversity and species composition

Marine Cyanobacteria as Sources of Lead Anticancer Compounds: A Review of Families of Metabolites with Cytotoxic, Antiproliferative, and Antineoplastic Effects

The marine environment is highly diverse, each living creature fighting to establish and proliferate. Among marine organisms, cyanobacteria are astounding secondary metabolite producers representing a wonderful source of biologically active molecules aimed to communicate, defend from predators, or compete. Studies on these molecules’ origins and activities have been systematic, although much is still to be discovered. Their broad chemical diversity results from integrating peptide and polyketide synthetases and synthases, along with cascades of biosynthetic transformations resulting in new chemical structures. Cyanobacteria are glycolipid, macrolide, peptide, and polyketide producers, and to date, hundreds of these molecules have been isolated and tested. Many of these compounds have demonstrated important bioactivities such as cytotoxicity, antineoplastic, and antiproliferative activity with potential pharmacological uses. Some are currently under clinical investigation. Additionally, conventional chemotherapeutic treatments include drugs with a well-known range of side effects, making anticancer drug research from new sources, such as marine cyanobacteria, necessary. This review is focused on the anticancer bioactivities of metabolites produced by marine cyanobacteria, emphasizing the identification of each variant of the metabolite family, their chemical structures, and the mechanisms of action underlying their biological and pharmacological activities

Una revisión sobre los dinoflagelados marinos bentónicos en México: Benthic dinoflagellates in Mexico

Background. Studies on marine benthic dinoflagellates (MBD) began in 1942 from the offshore region of Oaxaca, based on water column samples. Subsequently, in ten Mexican maritime states, both epibenthos and plankton samples have been collected, species have been cultured, and field and laboratory studies have been carried out. Many of these species are related to ciguatera fish poisoning and diarrhetic shellfish poisoning. Goals. The objective of this contribution was to review the studies on MBD in Mexican waters. Methods. Available literature on MBD published from 1942 to 2022 was analyzed. Results. A review of the studies on MBD is presented, subdivided into two sections: (1) taxonomic diversity (morphological and molecular) and (2) toxigenicity and species interactions. A map of the studies on MBD, a list of taxonomic and ecological studies on MBD in Mexico and a list of ca. 60 species (mainly Prorocentrum, followed by Amphidinium, Gambierdiscus, Ostreopsis and Sinophysis) is presented, accompanied by scanning electron microscopic images of 15 species. Knowledge of the toxigenicity of MBD is still scarce. Experimental studies on MBD begun in this century have shown great potential; Prorocentrum lima has been the main object of these studies. Conclusions. Studies on MBD have slowly increased, probably due to the availability of a greater number of strains, as well as to international collaboration. Confirmed links between particular benthic harmful algal blooming species and events associated with the etiology of toxic syndromes are rare. However, the lack of reports does not indicate an absence of intoxications. Studies on toxicity, allelopathy, ecology, impact on cultivated organisms, biosynthesis of metabolites and biotechnological potential still need to be undertaken in Mexico.Antecedentes. Los estudios sobre dinoflagelados bentónicos marinos (DBM) en México comenzaron en 1942 desde la región oceánica de Oaxaca, basados en muestras de la columna de agua. Posteriormente, en diez estados costeros mexicanos se recolectaron muestras de epibentos y plancton, se han cultivado especies, y se han realizado estudios de campo y de laboratorio. Muchas de estas especies están relacionadas con la intoxicación por consumo de peces (ciguatera) y la intoxicación diarreica por consumo de mariscos. Objetivos. El objetivo de esta contribución fue revisar los estudios sobre DBM en aguas mexicanas. Métodos. Se analizó la literatura disponible sobre DBM publicada desde 1942 hasta 2022. Resultados. Se presenta una revisión de los estudios sobre DBM subdividida en dos secciones: (1) diversidad taxonómica (morfológica y molecular) y (2) toxigenicidad y relaciones entre especies. Se presenta un mapa de los estudios sobre DBM, una lista de estudios taxonómicos y ecológicos sobre DBM en México y una lista de aproximadamente 60 especies (principalmente Prorocentrum, seguido de Amphidinium, Gambierdiscus, Ostreopsis y Sinophysis), acompañado de imágenes de microscopía electrónica de barrido de 15 especies. El conocimiento de la toxigenicidad de DBM aún es escaso. Los estudios experimentales sobre DBM iniciados en este siglo han demostrado un gran potencial, y Prorocentrum lima ha sido el principal objeto de estudio. Conclusiones. Los estudios sobre DBM han aumentado lentamente, probablemente debido a la disponibilidad de un mayor número de cepas, así como a la colaboración internacional. Los vínculos confirmados entre especies particulares de florecimientos algales nocivos bentónicos con los eventos asociados con la etiología de los síndromes tóxicos son escasos. Sin embargo, la falta de informes no indica ausencia de intoxicaciones. En México aún faltan por realizar estudios sobre toxicidad, alelopatía, ecología, impacto en organismos cultivados, biosíntesis de metabolitos y potencial biotecnológico

Morphological and Molecular Characterization of the Benthic Dinoflagellate <i>Amphidinium</i> from Coastal Waters of Mexico

The genus Amphidinium Clap. & J. Lachm. comprises a high diversity of planktonic and benthic (epiphytic and sand-dwelling) dinoflagellates from marine and freshwater ecosystems. High morphological plasticity and vaguely defined genus characteristics (e.g., a small epicone size) have complicated the clear delineation of species boundaries. Although six Amphidinium morphospecies have been reported from Mexican coastal waters, species identifications are uncertain and not generally supported by molecular phylogenetic data. In this study, seven isolates of Amphidinium from diverse benthic coastal locations on the NE Pacific, Gulf of California, and southern Gulf of Mexico were subjected to critical morphological analysis using photonic and scanning electron microscopy. The phylogenetic reconstruction was based on nuclear-encoded, partial large-subunit (LSU) rDNA and internal transcribed spacer I and II (ITS1 and ITS2) sequences. The revised phylogenetic analysis was consistent with the traditional subdivision of the genus Amphidinium into two sister groups: Herdmanii and Operculatum clades. This study provided the first confirmed records of A. theodorei and A. massartii from coastal waters of Mexico. The molecular phylogenetic evidence indicated that the morphologically described A. cf. carterae from Baja California was in fact more closely allied with A. eilatiensis sequences. A few Amphidinium species are known to form toxigenic (i.e., fish-killing) harmful algal blooms worldwide, and therefore knowledge on species diversity and biogeography is critical in developing effective strategies for evaluating the potential emerging threat in Mexican coastal waters