The role of microcystin

Toxic cyanobacterial blooms are a huge problem in freshwater. These blooms often result in beach closures because the toxins are harmful to humans and animals, and toxin contamination in drinking water can affect entire cities (like Toledo last summer). But what causes this problem? A recent publication from former lab member Lucas Beversdorf outlines some ideas. But first, let’s go over a little background about cyanobacterial toxic blooms.

– Cyanobacterial blooms are also called blue-green algae blooms or harmful algal blooms. However, cyanobacteria are NOT algae. Algae are more like single-celled plants, while cyanobacteria are true bacteria.

– Not all cyanobacteria produce toxins. In fact, most do not. So while large non-toxic blooms can cause other issues, they will not make you sick.

– The main toxin-producing genus of cyanobacteria is called Microcystis. Microcystis is capable of producing two types of toxin, microcystin (a neurotoxin) and cyanopeptolin (a peptide hepatotoxin).

Lucas’ paper addresses the question, “why produce toxins at all?” From an ecological standpoint, Microcystis gains no benefit from producing toxins that harm humans. Making chemicals is expensive for a cell – it must gain some benefit from the process. This paper shows that the nutrient ratios of carbon, nitrogen and phosphorus effect the production of microcystin in Lake Mendota. Specifically, toxic blooms are associated with periods when the amount of nitrogen available drops quickly. This may indicate that microcystin plays a role in the starvation response of Microcystis.

Read the full paper here


Beversdorf, Lucas J., Todd R. Miller, and Katherine D. McMahon. “Long-term monitoring reveals carbon-nitrogen metabolism key to microcystin production in eutrophic lakes.” Name: Frontiers in Microbiology 6 (2015): 456.

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