Unknown Extracellular and Bioactive Metabolites of the Genus Alexandrium: A Review of Overlooked Toxins

Abstract

Various species of Alexandrium can produce a number of bioactive compounds, e.g., paralytic shellfish toxins (PSTs), spirolides, gymnodimines, goniodomins, and also uncharacterised bioactive extracellular compounds (BECs). The latter metabolites are released into the environment and affect a large range of organisms (from protists to fishes and mammalian cell lines). These compounds mediate allelochemical interactions, have anti-grazing and anti-parasitic activities, and have a potentially strong structuring role for the dynamic of Alexandrium blooms. In many studies evaluating the effects of Alexandrium on marine organisms, only the classical toxins were reported and the involvement of BECs was not considered. A lack of information on the presence/absence of BECs in experimental strains is likely the cause of contrasting results in the literature that render impossible a distinction between PSTs and BECs effects. We review the knowledge on Alexandrium BEC, (i.e., producing species, target cells, physiological effects, detection methods and molecular candidates). Overall, we highlight the need to identify the nature of Alexandrium BECs and urge further research on the chemical interactions according to their ecological importance in the planktonic chemical warfare and due to their potential collateral damage to a wide range of organisms.

Short-Term Interactions of Noctiluca scintillans with the Toxic Dinoflagellates Dinophysis acuminata and Alexandrium minutum: Growth, Toxins and Allelopathic Effects

“…These were particularly harmful above 500 cells mL −1 , which corresponds with bloom densities in the field [ 21 ]. In the case of Alexandrium , it is known that most species produce bioactive extracellular compounds (BECs) which cause lytic effects on diverse organisms ranging from protists to mammalian cells [ 26 ]. BECs from A. catenella and A. minutum have been studied more in depth and include unknown large amphipathic compounds [ 26 ].…”

“…HABs involve a wide diversity of organisms with distinct population dynamics and mechanisms of impact [ 4 ]. Toxic effects and other deleterious consequences from HABs may involve several taxonomic groups [ 25 , 26 ], dinoflagellates being the most relevant—at least in terms of toxin production [ 27 ].…”

“…Allelochemicals are often related with benefits (i.e., through facilitating access to resources, inducing damage to protist competitors and defensive mechanisms) [ 26 ]. Thus, the consequences of the biotic interactions mediated by toxins and these compounds could contribute to explaining the ecological success of some dinoflagellates and HAB species in the field.…”

Toward a Predictive Understanding of Cyanobacterial Harmful Algal Blooms through AI Integration of Physical, Chemical, and Biological Data

“…This diversity explains the widespread occurrence of HABs at the global scale, underscored also by the variety of toxins and biological agents and the adverse effects within a given water ecosystem . For example, members of the genus Alexandrium (marine dinoflagellates) may have the capacity to produce saxitoxins, spirolides, goniodomins, unknown lytic molecules, etc., which affect the fauna of coastal areas. Conversely, a type of toxin, microcystin, can be produced by certain cyanobacteria of the genera Anabaena , Microcystis , and Planktothrix in freshwater lakes and reservoirs, and even on land after irrigation with contaminated water .…”

Apparent biogeographical trends in Alexandrium blooms for northern Europe: identifying links to climate change and effective adaptive actions

“…Some Alexandrium species also produce other bioactive compounds such as the cyclic imine spirolides (SPX) and gymnodimines (GYM), or goniodomin (GD) (Long et al, 2021;Murray et al, 2021). These bioactive metabolites can be "toxic" in some circumstances, but are considered as emerging toxins for further toxicological study.…”