OCT 24, 2023 11:39 AM PDT

Mycena Fungi Have Evolved to Infect Live Hosts

WRITTEN BY: Carmen Leitch

Mycena fungi are more commonly known as bonnet mushrooms, and they survive by consuming dead trees and plants. New research has determined that bonnets are also able to get into healthy young trees and plants, and they try to establish a cooperative relationship there. The study has suggested that this fungus has made an evolutionary adaptation that is now changing what we thought we knew about the ecology of fungi, an unusual group of organisms that is not easily classified.

The researcher and Mycena in the field. Credit: Christoffer Bugge Harder

Fungal spores can move through the air, looking for a good place to live. When they find those defenseless host locations, the fungi can use their new hosts to their own advantage. Although the television show The Last of Us has dramatized this kind of fungal growth and evolution in horrific ways, it's unlikely that humans are threatened by this organism. There are signs that Mycena are gaining new abilities, however. The findings have been reported in Environmental Microbiology.

Mycena fungi are in a fungal genus that has been thought of as saprotrophic because they consume dead organic stuff. But genetic work performed in this study showed that Mycena fungi are also a common presence in the roots of live plant hosts. "This suggests that bonnets are in the process of an evolutionary development, from uniquely being decomposers of nonliving plant material to being invaders of living plants, under favorable conditions," explained first study author Christoffer Bugge Harder of the University of Copenhagen.

Some species of bonnets are also showing the initial characteristics of organisms that can live in symbiosis with trees. But the fungi appear to be assisting the plants and trees, and not doing harm. For example, some Mycena seem to perform an exchange that provides plants with more of an essential nutrient - nitrogen.

Fungi have choices: they can become harmful parasites that drain the life from their hosts; they can hide away and wait for their plant host to die so they can consume the carcass; they can also decide to work with their host, as so-called mutualists. While more research will be needed to know for sure, it appears that some Mycena are becoming mutualists, noted Harder.

Fungi have traditionally been divided into groups based on whether they were mutualistic, parasitic, or saprophytic. Mycena won't be easily classified, however. The lines are starting to blur, strict divisions are being called into question, and some Mycena are spanning a variety of ecological roles, added Harder. An analysis of carbon isotopes in Mycena indicated that they have characteristics of mutualists, saprotrophic decomposers, and possibly parasites too.

Humans may have also encouraged these new developments in Mycena. "It is reasonable to believe that we humans have played a role in this adaptation, because our monocultural plantations, stands of forest for example, have provided fungi with optimal conditions for adapting. The fungi seem to have seized upon this opportunity," Harder suggested.

It may be possible for fungi to evolve in a way that enables them to live more closely with humans. After all, Candida auris has recently emerged and now causes many human infections. Fungi in tropical areas are also well adapted to high temperatures. But people should not be concerned about this new evolution of Mycena, because most people's immune systems can clear fungal infections, noted Harder. "So, I don't see any reason to fear fungi, or at least not worry about Mycena."

Sources: University of Copenhagen, Environmental Microbiology

About the Author
Bachelor's (BA/BS/Other)
Experienced research scientist and technical expert with authorships on over 30 peer-reviewed publications, traveler to over 70 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
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