Florida fungus combines psilocybin with deadly mushroom poison

Full text

A tiny brown mushroom found in Florida's swamps is the first known fungus to contain both psilocybin, the chemical compound in psychedelic mushrooms; and amatoxin, the poisonous substance in the world's deadliest mushrooms.

The species, Galerina indica, has been nicknamed the "dark magic mushroom" and was characterized in a study published Wednesday (Nov. 11) in the journal Current Biology .

"There is no species of mushroom anywhere, in any group, that has been known to produce both at the same time," study first author Andrew Kunik , a fungal biology researcher at the University of Florida, told Live Science. "So it's quite remarkable."

Exactly why the dark magic mushroom has evolved to contain these two compounds is unclear, but the authors told Live Science that they may give the fungus a powerful defense against being eaten.

Common evolutionary trick, rare combination

The ability to produce either psychedelic or toxic chemicals has evolved multiple times across fungal lineages . A process called horizontal gene transfer, which is widespread among fungi , has played a part in that process.

In horizontal gene transfer an organism passes new genetic material to another, as opposed to vertical gene transfer, in which a parent passes genetic material to offspring. It can lead to unexpected genetic combinations and, in bacteria, plays a key role in the development of antibiotic resistance .

The tiny mushrooms seem to have acquired both psychedelic and toxic compounds via horizontal gene transfer. (Image credit: Andrew R. Kunik) Some of the world's deadliest mushrooms, from the Amanita genus, stop cells from producing proteins and can cause death through liver failure. Past work has shown these mushrooms shared the ability to produce their poisonous amatoxins via horizontal gene transfer with mushrooms from the unrelated genera Galerina and Lepiota . Some mushrooms have acquired the ability to produce psilocybin via horizontal gene transfer as well.

But Kunik and colleagues weren't looking for specific chemicals when they began hunting for Galerina mushrooms in the swamps of Florida; they just wanted to learn more about the mushrooms' chemical makeup, as not all Florida Galerina mushrooms had been characterized before.

To find them both together in one mushroom, I never expected to find that.

Matthew E. Smith, plant pathologist at the University of Florida

They collected five specimens from Galerina , a genus that contains over 300 species worldwide, many of which are poisonous. Among the samples they collected were small G. indica specimens that grew on moss-covered palm trunks. The largest mushrooms were only about 0.2 inches (0.5 centimeters) tall, with caps up to about 0.1 inches (0.25 cm) wide.

Chemical analyses revealed that the dark magic mushroom contained both psilocybin and amatoxins, including one amatoxin that had never been documented in mushrooms. The new amatoxin wasn't wholly unexpected, given that other species of Galerina produce closely related amatoxins, Kunik said.

The production of psilocybin alongside the amatoxins was more of a surprise for the research team.

"To find them both together in one mushroom, I never expected to find that," study co-author Matthew E. Smith , a plant pathologist at the University of Florida, told Live Science. "We were shocked."

To understand how the tiny, deadly mushroom acquired its mind-altering, liver-poisoning abilities, the team compared the genes of G. indica with those of other psilocybin-producing mushrooms, finding the genes shared a common evolutionary origin — even though the mushrooms themselves are distantly related.

Scanning electron microscopy image of the spores from the “dark magic mushroom”. (Image credit: Andrew R. Kunik and Thomas E. Victor ) The researchers also found G. indica ’s psilocybin-producing genes are arranged in a different order than in other psilocybin-producing fungi, which suggests the gene cluster was rearranged during its evolutionary history, a clue that horizontal gene transfer happened.

Gene jumping and swapping

G. indica seems to have acquired the ability to produce psilocybin via horizontal gene transfer from unrelated fungi about 15.5 million years ago, based on reconstructions of Galerina ’s evolutionary history from DNA analysis, Smith said. However, it’s possible that psilocybin-producing genes entered the lineage through two separate horizontal gene transfer events, possibly as recently as 6 million years ago, Kunik noted. Collecting and sequencing more Galerina specimens could help untangle their evolutionary history.

The findings are surprising, said Hannah Reynolds , a fungal ecologist at Western Connecticut State University who was not involved with the new research. "What was exciting about this paper was seeing both of these [compounds] present, seeing that this gene cluster jumped in, got rearranged, maybe came in twice — it's very cool," Reynolds told Live Science.

Related stories

'It sounds so impossible': Student studying fungus that makes users hallucinate tiny people may be on the verge of a scientific breakthrough

1 psychedelic psilocybin dose eases depression for years, study reveals

Magic mushrooms temporarily 'dissolve' brain network responsible for sense of self

The ability to produce two types of incapacitating chemicals could form a powerful defense against being eaten, because organisms that would normally eat them would have difficulty evolving defenses against both, Kunik speculated.

But the idea that this duo of compounds prevents the mushroom from being eaten is just a hypothesis. To buttress that idea, further research might tweak the genes of the dark magic mushroom to observe how removing one compound affects the species' role in the food web, Kunik suggested.

Tropical and subtropical mushrooms are historically understudied, so there is likely much more incredible fungal diversity right under our feet, Smith said.