Salinity Affects Saxitoxins (STXs) Toxicity in the Dinoflagellate Alexandrium pacificum, with Low Transcription of SXT-Biosynthesis Genes sxtA4 and sxtG

Allelopathy between phytoplankton organisms is promoted by substances released into the marine environment that limit the presence of the dominating species. We evaluated the allelopathic effects and response of cell-free media of Chattonella marina var. marina and Gymnodinium impudicum in the toxic dinoflagellate Gymnodinium catenatum. Additionally, single- and four-cell chains of G. catenatum isolated from media with allelochemicals were cultured to evaluate the effects of post exposure on growth and cell viability. Cell diagnosis showed growth limitation and an increase in cell volume, which reduced mobility and led to cell lysis. When G. catenatum was exposed to cell-free media of C. marina and G. impudicum, temporary cysts and an increased concentration of paralytic shellfish toxins were observed. After exposure to allelochemicals, the toxin profile of G. catenatum cells in the allelopathy experiments was composed of gonyautoxins 2/3 (GTX2/3), decarcarbamoyl (dcSTX, dcGTX2/3), and the sulfocarbamoyl toxins (B1 and C1/2). A difference in toxicity (pg STXeq cell−1) was observed between G. catenatum cells in the control and those exposed to the filtrates of C. marina var. marina and G. impudicum. Single cells of G. catenatum had a lower growth rate, whereas chain-forming cells had a higher growth rate. We suggest that a low number of G. catenatum cells can survive the allelopathic effect. We hypothesize that the survival strategy of G. catenatum is migration through the chemical cloud, encystment, and increased toxicity.

Section: Discussionmentioning

confidence: 61%

Changes in Toxin Production, Morphology and Viability of Gymnodinium catenatum Associated with Allelopathy of Chattonella marina var. marina and Gymnodinium impudicum

Fernández-Herrera

Band‐Schmidt

Zenteno‐Savín

et al. 2022

“…Environmental variables, such as nutrients, salinity, temperature, and light intensity, influence the growth of Alexandrium cells, of which factors somehow affect STXs production [30,31]. For example, A. minutum has a substantially greater cellular toxin capacity when grown in phosphate (PO 4 )-depleted conditions [32].…”

Section: Environmental Factors Trigger Stxs Production Via Altering G...mentioning

confidence: 99%

“…For example, Malaysian A. minutum displayed high salinity tolerance (5-30 psu) [98], but A. tamiyavanichii and A. tamarense flourished in a 20-30 psu salinity range [99]. According to Bui et al (2021), the optimal salinity for A. pacificum isolated in Korea was recorded in the range of 30 and 35 psu [30], whereas A. insuetum showed maximal growth at 25 psu [100]. These show that different salinity tolerance ranges enable the strain to survive under salinity gradient conditions with different growth patterns [101].…”

Section: Salinity Modulates Stxs Production In Alexandriummentioning

confidence: 99%

“…Toxic Alexandrium species are one of the best model organisms for studying STX production, due to their toxicity, wide distribution, and negative impacts on marine habitats. Understanding how environmental conditions influence genetic traits and STXs production in Alexandrium is critical [30]. Therefore, this review focused on environmental factors that modulate STXs production by influencing the growth as well as metabolism of STX metabolites and related STX synthesis genes (sxt) in toxic Alexandrium.…”

Section: Introductionmentioning

confidence: 99%

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Environmental Factors Modulate Saxitoxins (STXs) Production in Toxic Dinoflagellate Alexandrium: An Updated Review of STXs and Synthesis Gene Aspects

Bui,

Pradhan,

Kim

et al. 2024

Self Cite

The marine dinoflagellate Alexandrium 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 (sxt) regulation in toxic Alexandrium, particularly in A. catenella, A. minutum, and A. pacificum. Hence, in this review, we focused on STXs production in toxic Alexandrium with respect to the major abiotic factors, such as temperature, salinity, nutrients, and light intensity. This review informs future research on more sxt genes involved in STXs production in relation to the abiotic factors in toxic dinoflagellates.

“…Phytoplankton are the chief contributor of toxins [7][8][9] and they are responsible for a variety of human ailments associated with seafood consumption [10]. They have been Toxins 2022, 14, 397 2 of 19 linked to episodic deaths in humans (1.5%) and other organisms, such as marine birds, mammals, and organisms dependent on the marine food web [11].…”

Section: Introductionmentioning

confidence: 99%

Toxic Effects and Tumor Promotion Activity of Marine Phytoplankton Toxins: A Review

Pradhan

Kim

Abassi

et al. 2022

Self Cite

Phytoplankton are photosynthetic microorganisms in aquatic environments that produce many bioactive substances. However, some of them are toxic to aquatic organisms via filter-feeding and are even poisonous to humans through the food chain. Human poisoning from these substances and their serious long-term consequences have resulted in several health threats, including cancer, skin disorders, and other diseases, which have been frequently documented. Seafood poisoning disorders triggered by phytoplankton toxins include paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning (ASP), diarrheic shellfish poisoning (DSP), ciguatera fish poisoning (CFP), and azaspiracid shellfish poisoning (AZP). Accordingly, identifying harmful shellfish poisoning and toxin-producing species and their detrimental effects is urgently required. Although the harmful effects of these toxins are well documented, their possible modes of action are insufficiently understood in terms of clinical symptoms. In this review, we summarize the current state of knowledge regarding phytoplankton toxins and their detrimental consequences, including tumor-promoting activity. The structure, source, and clinical symptoms caused by these toxins, as well as their molecular mechanisms of action on voltage-gated ion channels, are briefly discussed. Moreover, the possible stress-associated reactive oxygen species (ROS)-related modes of action are summarized. Finally, we describe the toxic effects of phytoplankton toxins and discuss future research in the field of stress-associated ROS-related toxicity. Moreover, these toxins can also be used in different pharmacological prospects and can be established as a potent pharmacophore in the near future.