Two artists working for ten years with bioluminescent organisms found a mushroom in Zurich that emits light in the dark. The phenomenon was studied and described in collaboration with a mycologist from the Federal Institute for Forest, Snow and Landscape Research (WSL).
It was while taking night photos in the Zurich-Albisrieden forest that Heidy Baggenstos and Andreas Rudolf noticed a green glow in their viewfinder.
Having the habit of looking at luminous organisms, the two artistes initially thought it was Mycena haematopusa known bioluminescent species.
But back in their workshop, it was found that it was Mycena crocataor orange milk mycena, a mushroom known for its saffron-colored latex, and which had never before been described as bioluminescent.
Luminous or bioluminescent mushrooms are often associated with tropical regions, but some also grow in Switzerland.
Sometimes bioluminescence is so faint that it is not visible to the naked eye: “Nowadays we always have our phone or a flashlight, but to see bioluminescence in the forest you have to It’s pitch black,” notes Andreas Rudolf.
Quantity of emitted light measured
In collaboration with Renate Heinzelmann, mycologist at WSL, the artists further characterized this new discovery, by measuring the quantity of light emitted by the different parts of the mushroom using long exposures and a luminometer, which amplifies the glows too weak for the camera.
“Most of the experiments were carried out by the artists. They collected the samples, took the photos and carried out the light measurements,” underlines the researcher, quoted in the WSL press release.
Luciferin and its chemical process
Bioluminescence is a chemical process by which living organisms produce light. Mushrooms have developed their own mechanism: the key step is the conversion of luciferin — from the Latin lucifer “which brings light” — by the enzyme luciferase into an unstable product, which releases energy in the form of light. Unlike fluorescence, this process does not require an external light source. Note that the luciferin has been discovered in more than 300 species capable of bioluminescence.
>> A photo gallery of luminous organisms by National Geographic: Bioluminescence
Brightness measurements revealed that Mycena crocata is not luminous except at the base of the stem, and that the mycelium was most often the source of the green light. This is why the rotting wood on which the fungus grows also emits a green glow which can last for four hours, until the wood dries out.
When Heidy Baggenstos and Andreas Rudolf established pure mycelium cultures under optimal conditions, bioluminescence lasted up to 164 days. Genetic experiments carried out by Renate Heinzelmann confirmed the identity of the species, as well as the presence of genes related to bioluminescence found in all luminous fungi of the genus Mycena.
“Bioluminescence is understudied, so the more we look, the more we will find,” concludes the researcher. With the two artists, she published this discovery in the specialized journal Mycoscience.
The mysterious role of bioluminescence
Bioluminescent fungi have fascinated people since Aristotle first observed them more than two thousand years ago, describing them as “cold fire” emanating from decaying wood, says the WSL.
Yet the mystery surrounding this phenomenon has persisted over time. Although the biological mechanism is now known, its ecological role remains uncertain. Although some bioluminescent fungi could attract insects to disperse their spores, this hypothesis does not apply to the bioluminescence of mycelium, well hidden underground.
“It seems that bioluminescence has been maintained for a long time; we therefore assume that it has a certain function,” notes the mycologist, “but the mystery remains.”
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