The Hidden Kingdom of Fungi

Exploring the Microscopic World in Our Forests, Homes, and Bodies

Keith Seifert

• Publisher: Greystone Books
• Year: 2022
• ISBN:
  9781771646635
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

"Fans of Merlin Sheldrake's Entangled Life and Suzanne Simard's Finding the Mother Tree will enjoy Seifert's latest... A perspective-shifting guide to our microfungal matrix."— Kirkus Even though we can't always see them, fungi exist all around us. From forests and farms to food and medicine—and even our homes and bodies—fungal connections shape how we live. In this illuminating book, readers will "discover how these marvels of nature enrich (and sometimes threaten) our lives."(Peter Wohlleben, New York Times -bestselling author of The Hidden Life of Trees.Esteemed career mycologist Keith Seifert reveals the important role that microscopic fungi, including yeasts, molds, and slimes, play in our lives, all while remaining invisible to the naked eye. Divided into sections, each one exploring a different environment where fungi thrive, The Hidden Kingdom of Fungi introduces readers to the fascinating world of mycology, with information on:

• How fungi are at the heart of life-changing medical breakthroughs, including the development of antibiotics such as penicillin and organ transplant drugs.

• Where fungi live in our homes and how they influence our health, from our gut to our scalps.

• How fungi add important vitamins to our diet and make our favorite foods and drinks possible, including wine, cheese, chocolate, and beer.

• The essential role fungi are playing in innovative technologies, such as creating alternative energy sources, reducing plastic pollution, cleaning up toxins from oil spills, and even building architecture for a Mars colony.

Despite their many benefits, we hold a precarious relationship with fungi: fungal diseases lead to over 1 million deaths each year, and they have played a destructive role in disasters ranging from the Irish Potato Famine to possibly even the extinction of the dinosaurs. The Hidden Kingdom of Fungi urges us to better understand our relationship with fungi—and to plan our future with them in mind—while revealing their world in all its beautiful complexity.

Part 1 The Hidden Kingdom

1 | Life in the Colonies Fungal Evolution

EARTH DID NOT ALWAYS LOOK like it does today. The land we stand on feels solid, but the continents float on molten magma like dumplings on a simmering stew. For the first billion years or so, most action on the planet was geological and chemical. The ancient, lifeless supercontinents drifted apart and bashed back together, most recently only a quarter billion years ago as a single landmass called Pangaea.

Life appeared about four billion years ago during the geological period we call the Precambrian Era. For the first two billion years, sometimes disparaged as the Boring Billions, all life-forms had just one cell. The atmosphere was a blend of nitrogen and carbon dioxide gases. Life is sweet: it’s all about sugar. A few bacteria discovered how to use sunlight to make sugar from the air by stitching carbon dioxide and water molecules together. This biochemical reaction, called photosynthesis, provides the food for all life. Oxygen was a by-product. As the millennia passed, the concentration of oxygen in the atmosphere climbed to 21 percent. Other microbes scrounged the waste secretions of these photosynthetic cells, survived on their tiny carcasses, or attacked living cells directly—life surviving off death by the processes of saprobic or parasitic nutrition.¹ Between 1 and 1.5 billion years ago, microbes with nuclei and multiple X-shaped chromosomes (known as eukaryotes) split into various kingdoms of life—including animals, fungi, plants, and several groups of protists.² The bacteria (often called prokaryotes), which have no nuclei and usually just one circular chromosome, went off on their own trajectory. Based on sheer numbers of cells and species, bacteria still dominate the modern world—but that’s a different story.

We think that the last common ancestors of animals and fungi were single cells that swam in the ocean with a whip-like flagellum (pl. flagella): microscopic tadpoles called zoo-spores. The ancestors of fungi were so tiny and fragile that only a few fossils exist that provide clues to what they looked like. Today, the surviving offshoots of this ancient evolution belong to the phylum Chytridiomycota, known as chytrids. The majority of the thousand or so species live a bucolic life in freshwater. Their zoospores wag their tails and flutter from place to place. They ram their way into pollen grains or the epidermis of floating seeds, like tiny goats butting a balloon. Then they swell up into one or a few cells that fill up with zoo-spores again. Some make finger-like cellular roots called rhizoids that grab on to or penetrate the host tissue. Sometimes zoospores smash their heads together and mate. You have probably never heard of chytrids (the name comes from the Greek for “little pot” and describes the mother cells filled with zoospores), but their affection for moisture and their habit of setting up zoospore factories in plants and animals lead to some serious diseases. The well-known amphibian apocalypse (see chapter 9) is one example.

Zygomycetes (“zygos” for short) were the next fungal group to split off, when modern multicellular life began to diversify and move onto land. Most modern zygos (now reclassified into several phyla; see appendix) are fast, weedy moulds like the compost mould Rhizopus. They search out moist, sugary nooks, pop up quickly, and saturate their surroundings with asexual spores. Quite a few are involved with insects. The familiar Entomophthora muscae glues houseflies to your windows each autumn and spatters a halo of white asexual spores around the corpse. The sexual process in zygo-mycetes is more like ours than most other fungi because there is only one child per mating. Pregnancy happens outside the body, though—the sexual zygospores swell up between the tips of a mating pair (see figure on p. 223). These dark, thick-walled balls are often covered with warts or elaborate branched projections that under a microscope give them the look of steel wool or the working end of a medieval flail. There is no mechanism for sending these spores elsewhere; they just drop into the dust and hibernate until favorable conditions return. Their dramatic ornamentation protects the spores from being devoured by hungry insect larvae and nematodes.

Root-associated zygos called arbuscular mycorrhizal fungi (see chapter 4) are among the fungi that helped plants adapt to life on land. Those cartoons of a fish squiggling out of the sea, growing legs, wobbling along, and transforming into a lizard, then a dinosaur, then some kind of ape, and finally, after millions of years, Homer Simpson—it didn’t happen like that. Although the details are lost to time, most land plants probably evolved from multicelled algae that migrated into freshwater, away from the salty violence of the sea. In that first few hundred million years, algae and fungi bobbed together in shallow ponds or dried together into crusts. The intimate cooperation and competition that still exists between the fungal and plant kingdoms bloomed.

Plants wouldn’t be as successful if they weren’t involved with fungi. Many cooperative relationships between fungi and plants developed and continued through the eons, eras, periods, epochs, and ages into the modern world. Hyphae—the thread-like cells that make up the bodies of fungi—grew inside plant leaves, stems, or roots. A few plant fossils have been found that give clues to these ancient relationships. Another strategy was for single-celled algae (or photosynthetic bacteria) to live inside colonies of a fungus, an arrangement we now call lichens.

The proliferation of fungi and land plants was dramatic and seemed to happen in sync. About 400 million years ago in the Devonian Period, the two largest fungal phyla of the modern world, Ascomycota (the ascomycetes) and Basidio-mycota (the basidiomycetes), appeared. Both interact intimately with living and dead plants, but in different ways.

Ascomycetes, or “ascos” for short, are the largest fungal phylum. You may know some of the conspicuous ones. Lumpy, coal-like, pricey truffles (Tuber species) nestle among the roots of oak trees. If dogs, wild pigs, or squirrels don’t find them first, you can dig them up and shave off some slivers to enhance your finest meals. Elusive wrinkled, egg-shaped morels (Morchella species, sometimes called Gucchi mushrooms) pop up in meadows and under trees for a few weeks each spring. They are prized by mushroom foragers, who often exhibit strong hoarding behaviors and keep their precious locations a secret.

Many of the roughly 87,000 known ascos are micro-scopic. You see them only as little dots or blobs on plants or animals. Or they hide away in decaying debris nibbling at the cellulose or starch, then bloom as an asexual, spore-spewing mould. Their sexual states are flask- or cup-shaped bodies that emerge from a nest of intermingled parental hyphae. Sexual spores form inside a larger sac-like cell called an ascus (pl. asci) that bulges out from the cell where the nuclei of the two parents merge. If the nucleus inside each ascus divides once, the fungus ends up with two ascospores per union; if twice, then 4, then 8, 16, 32, sometimes hundreds. The typical ascus, though, has eight neatly arranged ascospores and looks something like a transparent pod or sac full of beans. In most species, the asci are squirt guns: they rupture and a gush of cellular fluid propels the spores out into the air. Hundreds or thousands of asci may ripen at once, each the result of a unique union of nuclei from the original parent hyphae. It’s quite the orgy.

The ability to break down both cellulose and lignin in plants is a distinctive talent of many species of the other large fungal phylum, the basidiomycetes (“basidios”). About half of the fifty thousand species form what we generally consider mushrooms. Some have caps with gills, like the typical brown grocery store mushroom, Agaricus bisporus. Others have a spongy underside covered with tiny pores—boletes like the cep or porcini (Boletus edulis) adored by European mycophiles. Polypores (like the reishi mushroom, Ganoderma lucidum) are tough, woody bracket fungi that decay trees and lumber and have thousands of speck-like pores on the underside of their shelf-like structures. Puffballs are round fungal marshmallows about the size of a golf ball that soften with age and dispatch puffs of grayish spores into the air. (The giant puffball, Calvatia gigantea, swells to the size of a soccer ball and often gets treated like one.) Jelly fungi, like the yellow witch’s butter, Tremella mesenterica, often found on tree branches, swell into brain-like gelatinous masses when wet but shrink to a hard scab when dry. Some have yeasts as asexual states. Many microscopic basidiomycetes lurk in soil or plants too, notably the pathogenic rusts and smuts that can be so devastating to agriculture.

In many basidios, the hyphae arrange themselves into a miniature, concentrated mushroom in the soil and wait. When the showers come, the cells of this primordium inflate with liquid and a complete mushroom bursts out of the ground like a compressed sponge dropped into water. The force of this swelling can even break concrete. The gill or pore surfaces of the mature structure are covered by a layer of thousands of club-shaped microscopic cells called basidia where the nuclei originating with each parent merge. Each basidium is crowned with four tapering pins known as sterigmata. Each sterigma supports a developing basidiospore balanced off-kilter on its perch, and these spores inflate in synchrony to their final round or oval shape. Using a mechanism that involves the explosion of a tiny droplet of water, the spores pop off into the space between the gills and fall into the air current streaming around the cap.

Contemporary mycologists count about twenty phyla in the fungal kingdom.³ About sixteen of these groups contain only a few species and have little impact on humans. But the A, B, C, Zs—the ascomycetes, basidiomycetes, chytrids, and zygomycetes that we just met—together encompass millions of species. They display a vast range of beneficial and harmful behaviors that influence both nature and human civilization. To see them, you need only learn how to look.

Learning to See: Bringing Fungi Into the Light

How might you describe yourself on the telephone to the stranger who volunteers to meet you at the airport? I would be one of many slightly chubby, blue-eyed, shortish, middle-aged men with straight brown hair. You might need some special vocabulary to describe the shape of my nose, the mole above my lip, and the way I walk. It would be easier if we all wore name tags or had some kind of barcode.

For me, the process of learning to see the hidden world of fungi and distinguish its members started the summer after my second year at the University of Waterloo. In our survey course on nonvascular plants, I’d discovered an unexpected attraction to mycology and wanted to test-fly my new “expertise” on home turf. So at the end of the summer before third year, I stepped into the scraggly woodlot behind our house in Sudbury. I picked a few mushrooms but quickly realized I didn’t know much about them. The local bookstore had a single copy of just one guidebook, The Mushroom Hunter’s Field Guide, by the doyen of American mycology, Alexander H. Smith (1904-1986).⁴ To identify mushrooms, I discovered in that book, you make a spore print by resting a cap gill-side down on a piece of white or black paper and cover it overnight with a jar. Or better, half on white paper and half on black, so you can easily distinguish prints of white or black spores. The spores fall off the cap, and in the morning you can see what color they are.

After hours of navigating backwards and forwards in identification keys, and comparing my specimens with the bewildering jargon in the descriptions, I was 70 percent certain that what I had was the honey mushroom, Armillaria mellea. As the common and Latin names indicate, the caps are vaguely honey colored and have scales that look something like the crystals that form in old honey. According to the guide, an important distinguishing feature of honeys is the rhizomorph, a black shoestring-like strand found around the base. I tromped back into the ravine and scratched through the dirt with an intensity that gratified the dog, who was obviously pleased that I had learned something from her after all. Now that I knew what to look for, the rhizomorphs were everywhere, beneath the loose bark of rotting trees and meandering through the soil and leaf litter like long strips of black licorice. This made me more confident that I had the identity right. Honey mushrooms are also what Smith called “edible and choice,” a more enticing invitation than “boring but won’t kill you.” My goal was to show up my botanical sisters by bringing a wild mushroom to the table.

One rule of wild mushroom consumption is that the first time you eat any new species, you eat just a little. So I told my mother my plan and left most of the mushrooms untouched and the guide open at the appropriate page in case the poison control center needed them later. I heated up the skillet with a pat of butter and fried up one or two mushrooms. How bad could they be? They tasted okay, a bit like regular button mushrooms but with a slight metallic tang. I sat back to wait. Nothing unfortunate happened. Three weeks later, I was in the clear.

Mushroom guides are not shy about describing the dangers of mushroom poisoning.⁵ Although most mushrooms are not lethal to humans, the poisonous ones are surprisingly common. Different mushroom species make different toxins, and they affect the body in different ways. As soon as two hours after dining on a mushroom that causes gastric upset, but often as long as seven or eight hours, you vomit or scramble off to the toilet. Others take even longer to make you sick. The fatal effects of the kidney toxin orellanin, produced by Cortinarius orellanus and related species, are sometimes delayed by two or three weeks.

The beautiful, juicy-looking Amanita mushrooms seem to invite sampling, but species of this genus cause the most fatalities. Their common names convey the correct message. The white North American species Amanita bisporigera and the European A. virosa are known as destroying angels. The greenish to brownish A. phalloides, a European species spreading in North America since the 1930s, is called the death cap. So all mushroom pickers are taught to recognize Amanita first, before they learn the edible mushrooms in other genera. The Amanita toxins, circular peptides like amatoxin or phallotoxin, survive cooking and pass from the stomach into the bloodstream. Twelve to twenty-four hours later the unpleasantness begins, w...

Table of contents

• Cover
• Title Page
• Dedication
• Table of Contents
• Foreword
• A Note About Names
• Introduction: Diversity in the Dust
• Part 1: The Hidden Kingdom
• Part 2: The Fungal Planet
• Part 3: The Mycelial Revolution
• Acknowledgments
• Appendix: Fungal Classification
• Notes
• Literature Cited
• Index
• Copyright Page