The superpowers of mushrooms
They are neither plants nor animals, come in all sizes and possess surprising biological capabilities. We look at how mushrooms can be harnessed for the good of humanity.
Black mould (Aspergillus niger) can be used to produce colours and flavours. This is a coloured image of its fruiting body, seen under a scanning electron microscope. | Photo: Jannicke Wiik-Nielsen / Vetnist / Keystone / Science Photo Library
Tastes and colours
Fungi have been around for some 800 to 1,000 million years, so they have had time to adapt to all environments. This means there is no place on Earth – neither in the depths of the oceans, in the stratosphere, nor in our intestines – that they have yet to colonise. To overcome these diverse environmental constraints, they produce a rich panoply of molecules.
It’s precisely the richness of these elements that has often led them to end up in our food in the form of aromas and colourants. “The entire chromatic range can be reproduced thanks to mushrooms”, says Katia Gindro, the head of the mycology group at Agroscope. They naturally produce aromas too: vanillin, geraniol, coconut, musk… “Many lemon cakes sold in supermarkets achieve their flavour from the production of mushrooms”, she says. “And when we buy cheap vanilla, even if it contains an identical vanilla molecule, it is not produced from the well-known pods of the Vanilla planifolia orchid, but from a biotransformation process involving the mould Aspergillus niger and a woodland mushroom. This is a remarkable capacity with a role in nature still yet to be well understood”.
Many fungi live in the leaves of the mourou-mourou palm tree (Astrocaryum murumuru) that are presumed to prolong the tree’s life. | Photo: Marie Aucourd
Fed in exchange for their antibacterial effect
A large grouping of fungi, known as ‘endophytes’, live inside the tissue of plants. They exist there in symbiosis, taking advantage of sugar and water supplies. In exchange, they synthesise toxic metabolites that protect the plants from pathogens. Here we see the mourou-mourou palm tree native to Guyana, which hosts at least fifteen species of fungi.
Léonie Pellissier is a pharmaceutical science researcher at Agroscope who noticed the strong resilience of this plant with its long life-cycle and wondered if it was due to the presence of these fungal inhabitants. “We want to see if they have an antibacterial or anticancer interest”. Indeed, fungi frequently offer reservoirs of active molecules used in human medicine. Just take the example of penicillin, which launched the era of antibiotics, or cyclosporine, a vital immunosuppressant used when transplanting organs. In the fungi themselves, these metabolites generally favour survival or growth, although their exact role remains poorly understood.
Fungi are here turned into packaging materials. | Photo: Mycrobez
Custom high-tech builders
A mushroom colonises its environment by extending branched filaments outwards. This expansive growth is known as ‘mycelium’. It’s a dense network that binds to any particles it meets in two ways. First, there’s a physical entanglement, where the filaments trap the molecules they encounter. Secondly, in some cases, there’s also an adhesion between the mycelium and the particles in the environment, a form of natural glue.
This ability to bind particles is put to use at the EPFL’s sustainable materials laboratory, led by Tiffany Abitbol. In particular, they are taking advantage of species that degrade wood. “If we provide the mycelium with the nutrition and darkness it needs, it will proliferate and we can guide its development”. This means we can not only form it into any shape using moulds, but also bind it to certain particles of interest using physical aggregation. “It is possible, at this time, for us to manufacture a composite material by integrating particles that elicit a characteristic that the mycelium does not usually possess, e.g., strength or conductivity”. As a result, many mushroom-based materials have already seen the light of day in the form of products like sound insulators, textiles or packaging to replace traditional plastic.
This rye has been infested with the ergot fungus. | Photo: iStock
Against the mice, for the smiles
Claviceps purpurea, or rye ergot, is a mushroom that infects the eponymous cereal. It forms a dark violet mass where the grain would grow, then falls to the ground where it germinates come spring. This species produces lysergic acid, from which LSD, the hallucinogenic psychedelic, is derived. Jean-Luc Wolfender, a professor of pharmaceutical sciences at the University of Geneva, describes how the ecological roles of such molecules often remain mysterious, although not to the extent that theories don’t emerge: “The most well supported is that they prevent the mushroom from being eaten by rodents. The poor beasts do not come out of eating rye ergot well”.
In Homo sapiens, the controlled ingestion of LSD induces a modified state of consciousness. It brings about not only a change in perception but also a “loss of the boundaries of the ego”, something psychiatry uses as a starting point for certain therapies. The resulting decrease in activity in the amygdala – a region of the brain associated with fear – is also a promising avenue for the treatment of certain anxiety disorders and severe depression.
Here, daughter cells bud off their mother cell in baker’s yeast. In this image, taken with a scanning electron microscope, we can see the scars of previous cell divisions. | Photo: IKELOS GmbH / Dr. Christopher B. Jackson / Keystone / Science Photo Library
The simple complexity
“Phylogenetically, mushrooms are closer to animals than to plants,” says Markus Künzler, smiling. He studies mycelium at ETH Zurich and sees this genetic proximity as explaining why mushrooms have sophisticated genetic regulation mechanisms similar to ours. Where they differ from vertebrates is that they are devoid of vascular and nervous systems. Since the mushroom is a simple organism, despite possessing complex mechanisms, it has quickly become a valuable model to understand the living world.
Baker’s yeast, or Saccharomyces cerevisiae, is a simple and cheap unicellular fungus to cultivate and is therefore frequently used in laboratories. “It is a very popular model in cell biology”, says Künzler. “Much of our theoretical knowledge in biology was first established from this yeast, at that time from mammalian cells”. Included in the discoveries related to this fungus are the mechanisms controlling the cell cycle. That led to the attribution of the 2001 Nobel Prize and has direct applications in treating cancer in humans.
These common ink cap mushrooms use poisonous proteins to defend themselves against roundworms. | Photo: Muraguchi H. et al. (2011). With kind permission of the authors.
An organic pesticide
Fungivorous nematodes are all very small worms at two millimetres long. They have an arrow on their head that they plunge into the long filaments of the mycelium and use to suck out the contents of its cells. Faced with this attack, some mushrooms – e.g., the grey shag, or Coprinopsis cinerea, studied by the microbiologist Markus Künzler at ETH Zurich – synthesise specific toxic proteins. They are harmless to the mycelium and yet cause severe digestive disorders in an attacking worm leading potentially to its death. This is a defence system that fascinates Künzler: “The fungus detects the presence of attackers and alerts the still unexposed parts of the mycelium to preventively increase the production of toxins”.
This system could be used as an organic pesticide. Unlike otherwise persistent chemicals, these are proteins that break down quickly. Although practical applications remain complex precisely due to the fragility of the proteins, it is a promising avenue for agriculture.
