Algal Toxins

Dinoflagellates are a mixotrophic, sometimes toxic algae and are often ubiquitous members of harmful algal blooms (HABs). These diverse metabolites can exist as polyhydroxy polyenes and polyketides, alkaloids, and polyethers. Because of the diversity in their structures, dinoflagellate toxins can induce a variety of health effects including paralytic shellfish poisoning, neurotoxin shellfish poisoning, amnesic shellfish poisoning, diarrheic shellfish poisoning, and ciguatera poisoning. The risk that these toxins pose to human health and aquaculture industries warrants intense investigation.

Karlotoxin and Karlodinium veneficum

K. veneficum is a dinoflagellate present in the Chesapeake Bay known to produce karlotoxins that have hemolytic, ichthyotoxic, and cytotoxic properties. The toxins generated by K. veneficum have been implicated in massive fish kills during bloom events. 

The Place lab began working with K. veneficum in the 90s after a large mortality of striped bass occurred following copper sulfur treatment to arrest a dinoflagellate bloomon HyRock Fish Farm in Princess Anne, Maryland. While Pfiesteria sp. was initially suspected to be the cause behind the fish kill, the bloom was subsequently determined to be dominated by K. veneficum. Since then, the Place lab has been able to resolve the structures and absolute configurations for toxins that had been isolated previously. Additionally, our lab helped elucidate the mode of toxicity for these compounds after we found that additions of cholesterol inhibited the hemolysis of erythrocytes. 

The ichthyotoxicity of karlotoxins can be traced to its targeting the gills of fish and especially the chloride cells responsible for osmoregulation in fish. However, the Place lab has found that karlotoxin serves as both a mode of prey capture and a grazing deterrent for the algae. Luckily, K. veneficum is also associated with the parasitic dinoflagellate Amoebophyra sp. which could serve as a potential mitigation strategy for HABs. 

Feel free to listen or learn more with the provided audiobook and video resources. 

Amphidinol and Amphidinium carterae

A. carterae is another dinoflagellate that produces polyketide compounds (amphidinols) similar in structure to karlotoxins. This particular algae is less associated with algal blooms, but is often used as a model organism for its ability to be easily cultured in the laboratory under suitable temperature and light conditions.

The Place lab works regularly with this algae, using A. carterae and amphidinol as a model system to elucidate fatty acid and polyketide synthesis in dinoflagellates. Specifically, we have looked at the A. carterae transcriptome to better characterize the structure and abundance of polyketide synthesis domains. Additionally, the place lab has used cerulenin, a lipid synthesis disruptor, and acetate, a lipid synthesis substrate, to demonstrate the linkage between lipid synthesis and toxin synthesis pathways.

Most recently, we have been using Raman microscopy to identify where amphidinol is localized in A. carterae cells.

Toxin Production by Symbiotic Dinoflagellates