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Marine Environmental Research Jun 2024The bloom-forming dinoflagellate Alexandrium tamarense is one of the most important producers of paralytic shellfish poisoning toxins. Annually recurrent blooms of this...
The bloom-forming dinoflagellate Alexandrium tamarense is one of the most important producers of paralytic shellfish poisoning toxins. Annually recurrent blooms of this dinoflagellate species is associated with the incremental nitrogen influx, especially excessive nitrate input. However, limited studies have been conducted on the toxin production and underlying molecular regulation mechanisms of A. tamarense under various nitrate (N) conditions. Therefore, toxin production and transcriptomic responses of this species were investigated. The toxin profile of A. tamarense was consistently dominated by the C2-toxins, and the cellular toxicity increased with N concentrations peaking at 9.23 ± 0.03 fmol/cell in the 883 μM N-added group. Under lower N conditions, expressions of two STX-core genes, sxtA and sxtG, were significantly down-regulated, suggesting that N regulated sxt expression and triggered responses related to toxin biosynthesis. Results of this study provided valuable insights into the ecophysiology of A. tamarense, enhancing our understanding of the occurrence of toxification events in natural environments.
Topics: Dinoflagellida; Marine Toxins; Nitrates; Transcriptome; Water Pollutants, Chemical
PubMed: 38820827
DOI: 10.1016/j.marenvres.2024.106550 -
The Science of the Total Environment Jul 2024The innate immunity of bivalves serves as the initial defense mechanism against environmental pollutants, ultimately impacting genetic regulatory networks through...
The innate immunity of bivalves serves as the initial defense mechanism against environmental pollutants, ultimately impacting genetic regulatory networks through synergistic interactions. Previous research has demonstrated variations in the accumulation and tolerance capacities of bivalves; however, the specific mechanism underlying the low accumulation of PSTs in M. unguiculatus remains unclear. This study examined the alterations in feeding behavior and transcriptional regulation of M. unguiculatus following exposure to two Alexandrium strains with distinct toxin profiles, specifically gonyautoxin (AM) and N-sulfocarbamoyl toxin (AC). The total accumulation rate of PSTs in M. unguiculatus was 43.64 % (AC) and 27.80 % (AM), with highest PSTs content in the AM group (455.39 μg STXeq/kg). There were significant variations (P < 0.05) in physiological parameters, such as total hemocyte count, antioxidant superoxide activity and tissue damage in both groups. The absorption rate was identified as the key factor influencing toxin accumulation. Transcriptomic analyses demonstrated that PSTs triggered upregulation of endocytosis, lysosome, and immune-related signaling pathways. Furthermore, PSTs induced a nucleotide imbalance in the AC group, with total PSTs content serving as the most toxic indicator. These results suggested that protein-like substances had a crucial role in the stress response of M. unguiculatus to PSTs. This study provided novel perspectives on the impacts of intricate regulatory mechanisms and varying immune responses to PSTs in bivalves.
Topics: Animals; Dinoflagellida; Marine Toxins; Mytilus; Immunity, Innate
PubMed: 38796022
DOI: 10.1016/j.scitotenv.2024.173483 -
Toxins Apr 2024The marine dinoflagellate is known to form harmful algal blooms (HABs) and produces saxitoxin (STX) and its derivatives (STXs) that cause paralytic shellfish poisoning... (Review)
Review
The marine dinoflagellate is known to form harmful algal blooms (HABs) and produces saxitoxin (STX) and its derivatives (STXs) that cause paralytic shellfish poisoning (PSP) in humans. Cell growth and cellular metabolism are affected by environmental conditions, including nutrients, temperature, light, and the salinity of aquatic systems. Abiotic factors not only engage in photosynthesis, but also modulate the production of toxic secondary metabolites, such as STXs, in dinoflagellates. STXs production is influenced by a variety of abiotic factors; however, the relationship between the regulation of these abiotic variables and STXs accumulation seems not to be consistent, and sometimes it is controversial. Few studies have suggested that abiotic factors may influence toxicity and STXs-biosynthesis gene () regulation in toxic , particularly in , , and . Hence, in this review, we focused on STXs production in toxic with respect to the major abiotic factors, such as temperature, salinity, nutrients, and light intensity. This review informs future research on more genes involved in STXs production in relation to the abiotic factors in toxic dinoflagellates.
Topics: Dinoflagellida; Saxitoxin; Harmful Algal Bloom; Salinity; Shellfish Poisoning
PubMed: 38787062
DOI: 10.3390/toxins16050210 -
Toxins Apr 2024In Western Europe, the incidence of DST is likely the highest globally, posing a significant threat with prolonged bans on shellfish harvesting, mainly caused by species...
In Western Europe, the incidence of DST is likely the highest globally, posing a significant threat with prolonged bans on shellfish harvesting, mainly caused by species of the dinoflagellate genus . Using a time series from 2014 to 2020, our study aimed (i) to determine the concentration of in water at which shellfish toxin levels could surpass the regulatory limit (160 µg OA equiv kg) and (ii) to assess the predictability of toxic events for timely mitigation actions, especially concerning potential harvesting bans. The analysis considered factors such as (i) overdispersion in the data, (ii) distinct periods of presence and absence, (iii) the persistence of cells, and (iv) the temporal lag between cells in the water and toxins in shellfish. Four generalized additive models were tested, with the Tweedie (TW-GAM) model showing superior performance (>85%) and lower complexity. The results suggest existing thresholds currently employed (200 and 500 cells L) are well-suited for the Portuguese coast, supported by empirical evidence (54-79% accuracy). The developed algorithm allows for thresholds to be tailored on a case-by-case basis, offering flexibility for regional variations.
Topics: Dinoflagellida; Marine Toxins; Shellfish Poisoning; Shellfish; Animals; Portugal; Environmental Monitoring; Food Contamination
PubMed: 38787056
DOI: 10.3390/toxins16050204 -
Aquatic Toxicology (Amsterdam,... Jul 2024According to the results of the experimental study, the main regularities of changes in morphological, structural-functional and fluorescent indices of P. cordatum were...
According to the results of the experimental study, the main regularities of changes in morphological, structural-functional and fluorescent indices of P. cordatum were established when zinc oxide nanoparticles ZnO NPs (0.3-6.4 mg L) and Zn in form of salt (0.09-0.4 mg L) were added to the medium. The studied pollutants have cytotoxic (growth inhibition, development of oxidative stress, destruction of cytoplasmic organelles, disorganization of mitochondria) and genotoxic (changes in the morphology of nuclei, chromatin condensation) effects on microalgae, affecting almost all aspects of cell functioning. Despite the similar mechanism of action of zinc sulfate and ZnO NPs on P. cordatum cells, the negative effect of ZnO NPs is also due to the inhibition of photosynthetic activity of cells (significant decrease in the maximum quantum yield of photosynthesis and electron transport rate), reduction of chlorophyll concentration from 3.5 to 1.8 pg cell, as well as mechanical effect on cells: deformation and damage of cell membranes, aggregation of NPs on the cell surface. Apoptosis-like signs of cell death upon exposure to zinc sulfate and ZnO NPs were identified by flow cytometry and laser scanning confocal microscopy methods: changes in cell morphology, cytoplasm retraction, development of oxidative stress, deformation of nuclei, and disorganization of mitochondria. It was shown that the first signs of cell apoptosis appear at 0.02 mg L Zn and 0.6 mg L ZnO NPs after 72 h of exposure. At higher concentrations of pollutants, a dose-dependent decrease in algal enzymatic activity (up to 5 times relative to control) and mitochondrial membrane potential (up to 4 times relative to control), and an increase in the production of reactive oxygen species (up to 4-5 times relative to control) were observed. The results of the presented study contribute to the disclosure of fundamental mechanisms of toxic effects of pollutants and prediction of ways of phototrophic microorganisms reaction to this impact.
Topics: Zinc Oxide; Zinc Sulfate; Water Pollutants, Chemical; Oxidative Stress; Metal Nanoparticles; Microalgae; Dinoflagellida; Photosynthesis; Nanoparticles; Chlorophyll
PubMed: 38781690
DOI: 10.1016/j.aquatox.2024.106964 -
The Journal of Experimental Biology Jun 2024Marine heatwaves are increasing in frequency and intensity, with potentially catastrophic consequences for marine ecosystems such as coral reefs. An extended heatwave...
Marine heatwaves are increasing in frequency and intensity, with potentially catastrophic consequences for marine ecosystems such as coral reefs. An extended heatwave and recovery time-series that incorporates multiple stressors and is environmentally realistic can provide enhanced predictive capacity for performance under climate change conditions. We exposed common reef-building corals in Hawai'i, Montipora capitata and Pocillopora acuta, to a 2-month period of high temperature and high PCO2 conditions or ambient conditions in a factorial design, followed by 2 months of ambient conditions. High temperature, rather than high PCO2, drove multivariate physiology shifts through time in both species, including decreases in respiration rates and endosymbiont densities. Pocillopora acuta exhibited more significantly negatively altered physiology, and substantially higher bleaching and mortality than M. capitata. The sensitivity of P. acuta appears to be driven by higher baseline rates of photosynthesis paired with lower host antioxidant capacity, creating an increased sensitivity to oxidative stress. Thermal tolerance of M. capitata may be partly due to harboring a mixture of Cladocopium and Durusdinium spp., whereas P. acuta was dominated by other distinct Cladocopium spp. Only M. capitata survived the experiment, but physiological state in heatwave-exposed M. capitata remained significantly diverged at the end of recovery relative to individuals that experienced ambient conditions. In future climate scenarios, particularly marine heatwaves, our results indicate a species-specific loss of corals that is driven by baseline host and symbiont physiological differences as well as Symbiodiniaceae community compositions, with the surviving species experiencing physiological legacies that are likely to influence future stress responses.
Topics: Animals; Anthozoa; Species Specificity; Hawaii; Coral Reefs; Climate Change; Symbiosis; Hot Temperature; Photosynthesis; Carbon Dioxide; Dinoflagellida
PubMed: 38774956
DOI: 10.1242/jeb.246812 -
World Journal of Microbiology &... May 2024Bioactive compounds derived from microalgae have garnered considerable attention as valuable resources for drugs, functional foods, and cosmetics. Among these compounds,... (Review)
Review
Bioactive compounds derived from microalgae have garnered considerable attention as valuable resources for drugs, functional foods, and cosmetics. Among these compounds, photosynthetic pigments and polyunsaturated fatty acids (PUFAs) have gained increasing interest due to their numerous beneficial properties, including anti-oxidant, anti-viral, anti-bacterial, anti-fungal, anti-inflammatory, and anti-tumor effects. Several microalgae species have been identified as rich sources of bioactive compounds, including the Chlorophyceae Dunaliella and Haematococcus, the Bacillariophyta Phaeodactylum and Nitzschia, and the dinoflagellate Crypthecodinium cohnii. However, most of the reported microalgae species primarily grow through autotrophic mechanisms, resulting in low yields and high production costs of bioactive compounds. Consequently, the utilization of heterotrophic microalgae, such as Chromochloris zofingiensis and Nitzschia laevis, has shown significant advantages in the production of astaxanthin and eicosapentaenoic acid (EPA), respectively. These heterotrophic microalgae exhibit superior capabilities in synthesizing target compounds. This comprehensive review provides a thorough examination of the heterotrophic production of bioactive compounds by microalgae. It covers key aspects, including the metabolic pathways involved, the impact of cultivation conditions, and the practical applications of these compounds. The review discusses how heterotrophic cultivation strategies can be optimized to enhance bioactive compound yields, shedding light on the potential of microalgae as a valuable resource for high-value product development.
Topics: Microalgae; Heterotrophic Processes; Fatty Acids, Unsaturated; Biological Products; Dinoflagellida; Photosynthesis
PubMed: 38773011
DOI: 10.1007/s11274-024-03892-5 -
Journal of Cell Science Jun 2024Dinoflagellates are marine organisms that undergo seasonal proliferation events known as algal blooms. Vegetative cell proliferation is a main contributing factor in...
Dinoflagellates are marine organisms that undergo seasonal proliferation events known as algal blooms. Vegetative cell proliferation is a main contributing factor in these events. However, mechanistical understanding of mitosis and cytokinesis in dinoflagellates remains rudimentary. Using an optimized immunofluorescence protocol, we analysed changes in microtubule organization occurring during the mitotic cycle of the toxic dinoflagellate Ostreopsis cf. ovata. We find that the flagella and the cortical microtubule array persist throughout the mitotic cycle. Two cytoplasmic microtubule bundles originate from the ventral area, where the basal bodies are located - a cortical bundle and a cytoplasmic bundle. The latter associates with the nucleus in the cell centre before mitosis and with the acentrosomal extranuclear spindle during mitosis. Analysis of tubulin post-translational modifications identifies two populations of spindle microtubules - polar acetylated microtubules, whose length is constant, and central tyrosinated microtubules, which elongate during chromosome segregation. During cell division a microtubule-rich structure forms along the dorsal-ventral axis, associated with the site of cytokinesis, consistent with a cytokinetic mechanism that is independent of the actomyosin ring typical of animal and yeast cells.
Topics: Microtubules; Dinoflagellida; Mitosis; Cytokinesis; Spindle Apparatus; Cell Division; Tubulin
PubMed: 38770570
DOI: 10.1242/jcs.261733 -
Marine Pollution Bulletin Jun 2024An Alexandrium affine strain (AAJQ-1) from San José Island, Gulf of California was characterized for growth and toxicology. Fivefold of f/2 + Se cultures were...
An Alexandrium affine strain (AAJQ-1) from San José Island, Gulf of California was characterized for growth and toxicology. Fivefold of f/2 + Se cultures were incubated for 34 days in a temperature gradient (21-29 °C). Aliquots were collected every third day for cell counting, toxin determination, and nutrient analyses. In this study ELISA method was used to evaluate the PSP toxin production due to the lower detection limit than the HPLC method. The highest cell density (6724 cells mL) and growth rate (0.22 day) were obtained at 27 °C and they were related to temperature in all treatments. Cell density showed negative correlation with nitrate at temperatures ≥23 °C, and with orthophosphate 27 °C, furthermore, these correlations promote the toxin production (0.05-0.45 fmol STX cell); beyond that nitrite at high temperature seems to promote toxin production, which has not been sufficiently documented.
Topics: Dinoflagellida; Temperature; Marine Toxins; California; Nutrients; Seawater
PubMed: 38759464
DOI: 10.1016/j.marpolbul.2024.116464 -
Marine Pollution Bulletin Jun 2024Endosymbionts (Symbiodiniaceae) play a vital role in the health of corals. Seawater pollution can harm these endosymbionts and dispersants used during oil spill cleanup...
Endosymbionts (Symbiodiniaceae) play a vital role in the health of corals. Seawater pollution can harm these endosymbionts and dispersants used during oil spill cleanup can be extremely toxic to these organisms. Here, we examined the impact of oil and a specific dispersant, Corexit-9500, on two representative endosymbionts - Symbiodinium and Cladocopium - from the Southwestern endemic coral Mussismilia braziliensis. The survival and photosynthetic potential of the endosymbionts decreased dramatically after exposure to the dispersant and oil by ~25 % after 2 h and ~50 % after 7 days. Low concentrations of dispersant (0.005 ml/l) and dispersed oil (Polycyclic Aromatic Hydrocarbons, 1132 μg/l; Total Petroleum Hydrocarbons, 595 μg/l) proved highly toxic to both Symbiodinium and Cladocopium. These levels triggered a reduction in growth rate, cell size, and cell wall thickness. After a few hours of exposure, cellular organelles were damaged or destroyed. These acute toxic effects underline the fragile nature of coral endosymbionts.
Topics: Anthozoa; Animals; Symbiosis; Petroleum; Dinoflagellida; Water Pollutants, Chemical; Petroleum Pollution; Lipids; Surface-Active Agents
PubMed: 38754321
DOI: 10.1016/j.marpolbul.2024.116491