“If there is a rule in biology, I can think about how it does not apply to fungi,” Anne Pringle, a mycologist at the University of Wisconsin, Madison, said earlier this year. “They challenge our preconceptions of how biology works.” Neither plant nor animal (though closer to the latter in evolutionary terms), fungi are everywhere. They are, for the most part, invisible, single-celled microbes and cobwebs of wispy mycelial thread, lurking beneath the surface of things. Even those species that fruit, into the fleshy scallops, caps, and puffballs that we call mushrooms, tend to be frustratingly well-camouflaged. Scientists often describe fungi as cryptic. Their lifestyles are poorly understood, and their taxonomy is a mess. And yet, without them, biology would not work at all. Fungi are a forest’s sanitation department; in ecosystems across the globe, they break down and recycle organic matter, along the way supplying plants with nutrients, water, and chemical defenses.
In the course of making a podcast episode exploring the history and science of mushrooms, earlier this year, I became a confirmed mycophile, visiting mushroom farms, touring the U.S. National Fungus Collection, and voraciously consuming mushroom-related news, washed down with mugs of reishi tea. The elusive and unobtrusive nature of fungi means that we can only speculate as to how the year really went for them. As the composer and fungus fanatic John Cage wrote, “It’s useless to pretend to know mushrooms. They escape your erudition.” With that warning in mind, here are my fungal highlights of 2015.
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1. Geastrum britannicum
Each monthly issue of Mycosphere: The Journal of Fungal Biology contains descriptions of dozens of new species, from Leptosphaeria italica, found earlier this year on a dead branch in Italy, to a frilly, ridged parasol named Marasmius indopurpureostriatus, which was identified in the tiny Indian state of Sikkim, in the Himalayas. But the most endearing new fungus of 2015, Geastrum britannicum, was actually discovered by Jonathan Revett, an amateur mycophile, fifteen years ago, in the Fens of Norfolk, England. A patch of G. britannicum, with its dark brown spheres balanced on fleshy white bodies, looks uncannily like a huddle of little mushroom men, arms by their sides, buried in soil up to their waists. Scientists initially dismissed G. britannicum as a variant of another British mushroom, the rayed earthstar, which looks something like a starfish wearing a chef’s toque, but a recent DNA analysis established Revett’s specimen as distinct. “I wouldn’t normally question the experts, but I just knew these were different,” Revett told his local newspaper.
Elsewhere in 2015, scientists found new fungal species on salami and in the nests of leaf-cutter ants. Next year will undoubtedly bring its own fresh harvest. According to Lisa Castlebury, a research mycologist at the National Fungus Collection, of the more than one and a half million species that are estimated to exist, we have named and described only a hundred thousand.
2. Cordyceps
Members of the parasitic genus Cordyceps are sometimes referred to as zombie fungi, for their ability to control the behavior of insects and other arthropods. (The best-known zombie, Ophiocordyceps unilateralis, which belongs to a closely related genus, forces its ant host to hang on to the underside of a leaf while the fungus consumes its internal tissues, after which its mushrooms sprout from the ant’s empty husk.) Cordyceps also have a long history of use in traditional medicine, particularly in Asia; C. sinensis, for example, is known as Himalayan Viagra, and regularly sells for fifty thousand dollars a pound. Western medicine has been slower to embrace the zombie fungi, although the immunosuppressive drug cyclosporine, frequently used after organ transplantation, is derived from Cordyceps subsessilus, a devourer of beetles.
In 2009, Cornelia de Moor, a molecular biologist at the University of Nottingham, in England, discovered that cordycepin, a compound that is common to species in the Cordyceps genus, can halt the growth of cancerous cells in the lab, using a mechanism that is different from existing cancer treatments. This year, de Moor began trialling cordycepin as an osteoarthritis drug, because of its anti-inflammatory powers. If all goes well, physicians could be prescribing the new drug within the decade. (Which, presumably, is exactly what the fungus wants.)
3. When It Rains, It’s Spores
Cordyceps may be notorious for their powers of mind control, but, earlier this year, scientists found that fungi can also shape the weather. In a study published in the journal PLOS One in November, researchers at Miami University, in Ohio, demonstrated that airborne mushroom spores attract droplets of moisture, seeding clouds and then falling as raindrops. Nicholas Money, the study’s lead author, speculated that this may create a positive feedback loop, in which fungi whose growth is stimulated by rain catapult their spores into the air, only to encourage more rain. Millions of tons of fungal spores are released into the atmosphere every year, meaning that mushrooms likely have a significant effect on regional precipitation patterns—and their habitat destruction, Money concluded, could well lead to drought.
4. Yes, We Will Have No Bananas
Crop pathologists call Fusarium oxysporum, a tiny, asexual soil fungus, the “silent assassin.” It enters plants through their roots and travels through their vascular tissue; by the time it is ready to sporulate, the plant is doomed. The fungus has adapted to human agriculture by differentiating: F. oxysporum f. sp. lycopersici causes tomato wilt; F. oxysporum f. sp. asparagi causes asparagus wilt; and F. oxysporum f. sp. cubense is slowly but surely wiping out the world’s banana supply.
A particular strain of Fusarium, Tropical Race One, rendered the original globalized banana variety, the Gros Michel, commercially extinct in the first half of the twentieth century. Fortunately, the banana variety that fills our grocery stores today, the Cavendish, was resistant to Tropical Race One, and it eventually replaced the Gros Michel, although not before widespread banana shortages. Unfortunately, the Cavendish is not resistant to Tropical Race Four. The strain emerged in Taiwan in the late nineteen-sixties and has subsequently destroyed the banana industry in China, Indonesia, and Malaysia, and put a significant dent in the Australian harvest. Once a plantation is infected, there is no way to save the banana trees, and, because the fungus remains in the soil, the land cannot be used to raise bananas again. The only way to combat F. oxysporum f. sp. cubense is to make sure that it does not spread.
Last month, scientists at Wageningen University, in the Netherlands, published a paper that used genetic analysis to prove that a single clone of Tropical Race Four is responsible for infecting banana plantations on multiple continents. The significance of the Dutch research is that it shows that strict quarantine and biosecurity measures have failed to stop Tropical Race Four’s spread—meaning, as the authors write, that the fungus’s arrival in the banana-growing regions of Central America is a question of “when, not if.” This time, there is no Fusarium-resistant replacement waiting in the wings.
5. Bespoke Yeast
Yeasts win fungus of the year every year, at least from the human point of view—wine, bread, and beer insure that. But 2015 was the year of designer yeast. Yeasts normally consume sugar and excrete carbon dioxide and alcohols, but new gene-editing technologies such as CRISPR have made it much easier and faster to insert strands of functional DNA from other organisms into the yeast genome, transforming its metabolism. The result is a cell-size factory that can pump out anything from flavorings to pharmaceuticals. This year, yeasts capable of producing spider silk, morphine, and palm oil all made their débuts—early signs, perhaps, of a transition from an economy based on agriculture and hydrocarbon chemistry to one run on fungi.
