Artists Uncover Bioluminescent Mushroom in Switzerland

Bioluminescent fungi have fascinated people since Aristotle first observed them more than 2,000 years ago, describing them as a “cold fire” emanating from decaying wood. Yet the mystery surrounding the phenomenon has persisted throughout the The mechanisms behind this ability of certain organisms to produce light are only beginning to be well understood. Although associated with tropical regions, it also occurs in temperate environments, as recently demonstrated. by researchers from the Federal Institute for Forest, Snow and Landscape Research (WSL) in Switzerland, on a mushroom.

Published in the journal Mycoscience, this research reveals an unexpected property in Mycena crocata, a mushroom common in Europe and Asia. Identified thanks to a collaboration with Zurich artists, this bioluminescence, which has remained invisible until now, raises questions about its ecological functions and its evolutionary implications. This discovery highlights unexplored aspects of fungal biodiversity in European forests, stimulating new perspectives on a largely unknown phenomenon.

A light in the darkness: the emergence of a mushroom

During evening walks in the forests of Albisrieden, a district of Zurich, artists Heidy Baggenstos and Andreas Rudolf, accustomed to exploring bioluminescent organisms, spotted a faint green glow emanating from a mushroom. The observation, carried out with a camera in the total absence of artificial light, revealed a phenomenon imperceptible to the naked eye under normal conditions. The artists initially thought they had discovered Mycena haematopusa species known for its luminous properties. However, after further analysis in their studio, they quickly identified Mycena crocata. The problem is that this fungus is known to be non-bioluminescent, despite its widespread presence in European forests. This unexpected discovery then motivated an in-depth scientific investigation.

M. crocata in light (left) and in darkness (right). The bioluminescence of the mycelium makes the wood glow. © Baggenstos/Rudolf

With the support of Renate Heinzelmann, mycologist at WSL, the luminous properties of Mycena crocata were confirmed. Genetic analyzes revealed that this species has genes related to bioluminescence. These genes are found to be similar to those of other bioluminous fungi. This mushroom grows mainly on the debris of beech trees and other hardwoods. It produces a diffuse green light from its mycelium, the underground part responsible for nutrient absorption. This property, still largely unknown, requires specific conditions to be observed and studied with precision and modern tools. However, increasing light pollution compromises these observations and discoveries. “ Today we always have our cell phone or flashlight with us, but to see bioluminescence in the forest it has to be dark », Supports Rudolf.

Scientific analysis of the mushroom: an elusive light

The artists measured the amount of light emitted by different parts of the mushroom using long exposure photographs and a luminometer. This amplifies weaker light than a camera. “ Most of the experiments were carried out by the artists. They collected the samples, took the photos and carried out the light measurements », recognizes Heinzelmann. The bioluminescence observed in Mycena crocata is therefore limited to specific areas of the fungus. Researchers have established that this subtle green glow is generated by a biochemical process specific to luminous mushrooms. This involves the transformation of luciferin into an unstable molecule by the enzyme luciferase. This reaction produces energy in the form of light without requiring an external source.

Involving a sequence of complex biochemical steps, now largely elucidated, they vary in their intensity and distribution depending on the species. A fascinating aspect of this bioluminescence is that decomposed wood, when inhabited by the mycelium of M. crocatacan also emit green light when split. A temporary phenomenon, fading quickly as the wood dries out.

Work carried out in the laboratory has confirmed the robustness of this light mechanism. By growing the mycelium under controlled conditions, the researchers found that bioluminescence could be maintained for 164 days. Exceptional duration compared to other bioluminescent organisms. This result demonstrates the stability of this process in M. crocata in a favorable environment. However, the low intensity of the emitted light poses a challenge for its detection in nature, where it is often masked by ambient light variations. This characteristic explains why the bioluminescence of this species has remained unknown until now.

The mysteries of fungal bioluminescence

Despite advances in understanding the chemical mechanisms behind bioluminescence, its ecological role remains a mystery. In some fungal species, intense bioluminescence attracts nocturnal insects. It thus facilitates the dispersion of spores. However, this function seems unlikely for Mycena crocata. Indeed, the spores are mainly dispersed by the wind. The light emitted by this species being weak, localized, and often invisible to the human eye, makes its interaction with pollinators or other potential vectors difficult. The evolution of this phenomenon seems to indicate an alternative function. For the authors, light could serve purposes not yet identified. Perhaps interactions with microorganisms or internal processes related to the survival of the fungus in specific environments.

M. crocata in Albisrieden, Zurich. © Baggenstos/Rudolf

Highlighting the bioluminescent properties of Mycena crocata then opens perspectives on the existence of other species of the same genus whose luminous capacities remain unknown. Recent analyzes have revealed that several fungi Mycenaconsidered non-luminous, nevertheless possess the genes necessary for bioluminescence. This suggests a significant underestimate of the true number of bioluminescent species within this group. The difficulty of detecting this faint light in nature, combined with a lack of thorough investigation, contributes to this bias. Researchers are calling for a systematic exploration of mushroom species, using modern tools like luminometers and high-sensitivity cameras. We could thus better understand the distribution and evolutionary functions of this unique phenomenon in forest ecosystems.

Source: Renate Heinzelmann et al., “Is the bioluminescence in many Mycena species overlooked? ― A case study from M. crocata in Switzerland”, Mycoscience (2024)