Medical applications of cyanobacteria toxins

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Written by: Sam Hulme

When talking about toxins, perhaps the first thing that comes to mind is to keep a healthy distance from them. This train of thought seems very logical and is undoubtedly very effective at preventing from poisoning yourself. However, a number of different studies into the potential medicinal benefits of certain toxins have shown that we still have much to learn in this field. In this blog, I shall explore and discuss the medical applications of toxins produced by marine algae known as cyanobacteria.

Cyanobacteria are found across the globe in both saltwater and freshwater systems. There are many different types of cyanobacteria, and many of them produce toxins known as cyanotoxins. Some of these cyanotoxins are very dangerous to humans if ingested, and on numerous occasions have proven to be fatal to dogs which have consumed them.1 Many rivers in New Zealand have been seasonally infested with toxic cyanobacteria, forcing local councils to enforce a ban on swimming when the blooms of cyanobacteria are especially large to ensure the public’s health and safety. Now that we know a little bit about the negative effects of toxic cyanobacteria, let us look at these algae from a different perspective – a medical perspective to be precise.

As well as producing cyanotoxins, cyanobacteria produce something called secondary metabolites. Secondary metabolites are produced in order to provide more favourable growth conditions for the cyanobacteria by inhibiting the growth of other organisms competing within the same system.2 A well-known example of a secondary metabolite commonly used in medicine is an antibiotic, which is used to treat bacterial infections by limiting or preventing the growth of bacteria.3

There has been a lot of interest in secondary metabolites produced by cyanobacteria which have anticancer properties. The most common form of cancer treatment currently used is chemotherapy, though it has a limited effectiveness which can be attributed to the potentially fatal side effects as well as cancer cells building up a resistance to the drugs used during treatment.4 A study published in 2018 by the International Journal of Molecular Sciences states that the anticancer agents found within cyanobacteria have been essential in the development of new pharmaceutical drugs used for cancer treatment, with numerous successful cases reported during clinical trials.5 There are still a vast number of anticancer agents produced by cyanobacteria which are being clinically trialled, hopefully implying that our ability to treat cancer improves significantly in the near future.

Interestingly, the medical applications of cyanotoxins does not apply only to humans. In a study conducted at the University of Michigan, small freshwater crustaceans called Daphnia (commonly known as water fleas) were monitored after consuming cyanotoxins. The study shows that after ingesting these cyanotoxins, the Daphnia developed protection from fungal parasites.6 This example of self-medication highlights the importance of cyanobacteria blooms to marine ecosystems.

In conclusion, I believe that despite some of the negative effects of cyanobacteria on humans, they have proven to be a fascinating area of study which has been very rewarding to medical science. With antibiotic, anticancer, and antifungal agents being produced by these unassuming blooms of algae, I am very excited to see what other uses may be discovered for the benefit of medical science going into the future.


1. Cardwell, H. (2018). Dogs die in worst year for Hutt River blooms. Retrieved from

2. Demain A.L., Fang A. (2000) The Natural Functions of Secondary Metabolites. In: Fiechter A. (eds) History of Modern Biotechnology I. Advances in Biochemical Engineering/Biotechnology, vol 69. Springer, Berlin, Heidelberg.

3. Microbiology Society. (n.d.). Antibiotics. Retrieved March 3, 2021 from,by%20soil%20bacteria%20and%20fungi.

4. Mahdi, E., & Fariba, K. (2012) Cancer treatment with using cyanobacteria and suitable drug delivery system. Annals of Biological Research, 3 (1):622-627. Retrieved from

5. Seca, A., & Pinto, D. (2018). Plant Secondary Metabolites as Anticancer Agents: Successes in Clinical Trials and Therapeutic Application. International journal of molecular sciences19(1), 263. Arbor, A. (2019). Poisons or medicines? Cyanobacteria toxins protect tiny lake dwellers from parasites. NewsRx Health & Science, 280.