Ergot Alkaloids (EAs) belong to a large class of mycotoxins. They are primarily produced by fungi in the genera Claviceps and Epichloë, although Claviceps purpurea is responsible for most of the impacts on humans. EAs are most common in rye, but can be found in any cereal grain. The toxins were a significant problem in the middle ages, but modern agricultural techniques mean that exposure to enough EAs to cause symptoms is extremely rare.1,2 Sources Many fungi produce ergot alkaloids in many different plant hosts. Humans are impacted most by species of Claviceps, which infect seeds of grasses. The most problematic species is C. purpurea (see FFF#061), which infects rye. A variety of other species infect cereal grains but cause less contamination. Livestock can be sickened by infected grain or by ergot alkaloids produced by endophytes in pasture grasses, most notably by Epichloë coenophiala.1–3 This post focuses on Claviceps and...
Fungus Fact Friday
You are undoubtedly familiar with this mushroom, even if you recognize neither its scientific name, Amanita muscaria, nor its common name, “The Fly Agaric.” If the word “mushroom” does not immediately bring this fungus to mind, then the word “toadstool” probably does. You have certainly encountered A. muscaria’s distinctive red cap with white spots in a variety of visual art forms. This toadstool frequently pops up in paintings, cartoons, video games, movies, and decorations. Essentially, A. muscaria is the default mushroom that people (in Western societies, anyway) think of when they hear the word “mushroom” – the type specimen for mushrooms, if you will. This is probably best illustrated by the Wikipedia page for “Mushroom,” which features a prominent picture of the photogenic Fly Agaric. Morphology Amanita muscaria produces large, umbrella-shaped agaric mushrooms with a circular, brightly colored pileus and a central, white stipe. The pileus ranges in size from...
Unlike most other mycotoxins found in food, the ochratoxins are primarily produced during food storage. Fungi in the genera Aspergillus and Penicillium are common molds that decompose a variety of foods, from grains to coffee to grapes. In the process, many of those fungi produce ochratoxins, which can damage the kidneys and cause cancer in many animals. Ochratoxins presumably impact humans the same way, but researchers have so far been unable to directly link ochratoxins to any human disease. This is probably because human consumption of ochratoxins is usually very low.
Zearalenone is a fascinating mycotoxin produced by Fusarium species. It is the only mycotoxin that mimics the effects of the hormone estrogen. In high doses, it causes sexual organs to develop incorrectly. Pigs are the most susceptible animals and suffer estrogenism and vulvovaginitis when exposed to high levels of zearalenone. The toxin is present in many grain-based foods intended for human consumption, but usually at very low levels. As a result, zearalenone is generally harmless to humans.
Humans have very little to worry about from fumonisins, mycotoxins produced by Fusarium fungi that cause Fusarium ear rot disease of corn (maize). The toxins are linked with esophageal cancer, but scientists cannot prove that they cause cancer. However, fumonisins are a major problem for horses and pigs. In horses, the toxins cause liquefaction of the brain tissue, while in pigs they cause the lungs to fill with water.
In honor of the recent Thanksgiving holiday, I chose to rework this post on the Turkey Tail. I will continue discussing mycotoxins next week. It is easy to see why Trametes versicolor is commonly called the “Turkey Tail”: the upper surface of the fan-shaped polypore sports rings of color that vary from gray to brown to reddish-orange. In fresh specimens, the edge of the mushroom is white, making it look remarkably like the displayed tail of a wild turkey. T. versicolor is a very common decomposer and produces mushrooms that are visible all year, so you can probably find it the next time you walk through the woods.
Deoxynivalenol (DON) is a toxin found in grains infected with the fungus Fusarium graminearum and other Fusarium species. It is often called “vomitoxin” because it primarily causes vomiting in humans and livestock. Its long-term effects are mild, but it is still a very important mycotoxin because it is the most common mycotoxin found in food.
Fungi produce innumerable “mycotoxins” – compounds that are toxic to humans. In mushrooms, these cause symptoms ranging from gastrointestinal upset to death (see FFF#091–100 for more). Although these are of significant concern to mushroom hunters, their impact is relatively small. The most significant mycotoxins in terms of the number of people affected are produced by molds that naturally grow on food. Over the next few weeks, I will discuss some of the most problematic food-borne mycotoxins. Topping that list are the aflatoxins, which cause liver cancer and are especially problematic for people in developing nations.
Fungi appear in the news with surprising frequency. However, many of those stories do not provide any new information. Below is a summary of what we’ve learned about fungi from August through October 2017. Read below to learn about: ballistospory, chromosome evolution, fighting fungal pathogens (in humans, bats, and bananas), psilocybin, oil-eating fungi, and more! Visit the associated links to get the full story.
If the spirit of Halloween were a mushroom, it would be Omphalotus illudens. This agaric is commonly known as the “Jack-O-Lantern mushroom” for a few good reasons. First, it is bright orange, like the pumpkins that decorate doorsteps all over the United States in October. Not only is the cap orange, but so are the gills, the stipe, and the interior. Second, the mushroom’s gills glow in the dark, especially when they are young and fresh. Furthermore, the mushroom often has a sweet smell and is poisonous. Nothing says Halloween like something that is orange, glows in the dark, smells sweet, and has a sinister side.