Table of Contents

What Is Mycology?

Mycology is the branch of biology that studies fungi — a kingdom of organisms that includes mushrooms, molds, yeasts, and thousands of less familiar species. If that sounds like a niche topic, consider this: without fungi, terrestrial life as we know it almost certainly wouldn’t exist. They decompose dead matter and recycle nutrients. They form partnerships with about 90% of all plant species. They gave us penicillin, bread, beer, and cheese. And we’ve barely scratched the surface of understanding them.

Fungi aren’t plants, aren’t animals, and aren’t bacteria. They occupy their own kingdom of life — and they’re actually more closely related to you, genetically speaking, than they are to any plant. That fact surprises most people, but it’s been well established since molecular phylogenetics reshaped our understanding of life’s family tree in the late 20th century.

Fungi Are Not What You Think

The biggest misconception about fungi is that mushrooms are the organism. They’re not. A mushroom is to a fungus what an apple is to an apple tree — just the reproductive structure. The actual organism is the mycelium, a vast network of thread-like cells called hyphae that spread through soil, wood, leaf litter, or whatever substrate the fungus inhabits.

These hyphal networks can be enormous. The largest known organism on Earth is an Armillaria ostoyae (honey fungus) in Oregon that covers about 2,385 acres — roughly 1,665 football fields. Most of it is underground, invisible. It’s estimated to be somewhere between 2,400 and 8,650 years old.

A single cubic inch of healthy forest soil can contain eight miles of hyphal threads. Let that sink in. The ground beneath a forest is threaded with an almost incomprehensibly dense network of fungal cells, all actively breaking down organic matter, exchanging nutrients with plant roots, and communicating chemical signals.

How Fungi Feed

Here’s the fundamental difference between fungi and plants: plants make their own food through photosynthesis. Fungi can’t. They lack chlorophyll entirely. Instead, fungi are heterotrophs — they get energy by absorbing nutrients from external sources.

But they don’t eat the way animals do. Animals ingest food and digest it internally. Fungi do it backward: they secrete digestive enzymes outside their bodies, breaking down complex organic molecules in their environment, then absorb the resulting simpler molecules through their cell walls.

This extracellular digestion strategy is why fungi are the planet’s champion decomposers. They can break down lignin (the tough structural polymer in wood) and cellulose (the main component of plant cell walls) — feats that most organisms can’t manage. Without fungal decomposition, dead trees and plant matter would simply accumulate, and the carbon and nutrients locked inside them would never return to the ecosystem.

The Three Lifestyles

Fungi generally fall into three ecological categories:

Saprotrophs feed on dead organic matter. These are the recyclers — the fungi that decompose fallen trees, dead leaves, animal remains, and other organic debris. Without saprotrophic fungi, forests would drown in their own detritus within a few years.

Parasites feed on living organisms, often causing disease. Fungal parasites attack plants (causing blights, rusts, and smuts that can devastate crops), animals (athlete’s foot, ringworm, and more serious systemic infections), and even other fungi. The chestnut blight fungus (Cryphonectria parasitica) essentially eliminated the American chestnut from eastern North American forests in the early 20th century — one of the most dramatic ecological disasters in recorded history.

Mutualists form partnerships with other organisms where both parties benefit. The most important of these partnerships — arguably the most important biological relationship on Earth — is the mycorrhizal association between fungi and plant roots.

The Wood Wide Web — Mycorrhizal Networks

About 90% of all land plants form mycorrhizal associations with fungi. The plant provides the fungus with sugars produced through photosynthesis. The fungus, in return, extends the plant’s root system dramatically — hyphal networks can increase a root system’s effective surface area by 100 to 1,000 times — and delivers water and mineral nutrients (especially phosphorus and nitrogen) that the plant’s roots alone couldn’t access.

This isn’t a minor relationship. It’s foundational to how terrestrial ecology works.

Mycorrhizal networks connect multiple plants through shared fungal highways. A large tree might be connected, through mycorrhizal fungi, to hundreds of other plants — including different species. Research has shown that these networks can transfer carbon, nitrogen, phosphorus, water, and even chemical defense signals between connected plants.

Ecologist Suzanne Simard’s research on these networks (popularized as the “Wood Wide Web”) demonstrated that large “mother trees” in a forest can funnel carbon to smaller seedlings through mycorrhizal connections, effectively subsidizing the next generation’s growth. When a tree is dying, it sometimes transfers a burst of carbon to its neighbors through the network — almost like a biological last will and proof.

This has reshaped how ecologists think about forests. A forest isn’t a collection of individual trees competing for resources. It’s an interconnected community, with fungi serving as the communication and transport infrastructure.

A Brief History of Mycology

Humans have used fungi for thousands of years — bread, beer, and fermented foods all depend on yeast, a single-celled fungus. But scientific mycology is relatively young.

Early Observations

The ancient Greeks and Romans knew about mushrooms, though they didn’t understand what they were. Theophrastus (371-287 BCE) mentioned truffles and mushrooms in his botanical works, classifying them as plants. This misclassification persisted for over 2,000 years.

The Microscope Era

When Antonie van Leeuwenhoek and Robert Hooke started looking through microscopes in the 1660s and 1670s, they observed fungi at a cellular level for the first time. The Italian scientist Pier Antonio Micheli published Nova Plantarum Genera in 1729, which is often considered the founding work of modern mycology. Micheli demonstrated that fungi reproduce via spores — not by spontaneous generation, as was commonly believed.

Classification Struggles

For centuries, fungi were classified as plants. They grow from the ground, they don’t move, they seem plant-like. But as biology advanced, the differences became impossible to ignore. Fungi don’t photosynthesize. Their cell walls contain chitin (the same material in insect exoskeletons) rather than cellulose. Their cellular organization, biochemistry, and genetics are distinct from plants.

In 1969, Robert Whittaker proposed the five-kingdom classification system, finally giving fungi their own kingdom. Molecular evidence in the 1990s and 2000s confirmed that fungi are more closely related to animals than to plants — a finding that still catches people off guard.

The Modern Era

Contemporary mycology has been transformed by DNA sequencing. Before molecular tools, mycologists classified fungi primarily by their physical characteristics — spore shape, cap color, gill structure. This led to many misclassifications because distantly related species can look similar (convergent evolution), and closely related species can look different.

DNA barcoding — identifying species by short, standardized genetic sequences — has revolutionized fungal taxonomy. Environmental DNA (eDNA) sampling allows mycologists to detect fungal species in soil, water, and air without ever seeing the organism itself. The result has been an explosion of newly described species and a wholesale rearrangement of fungal family trees.

The Major Groups of Fungi

Fungi are extraordinarily diverse. The major groups include:

Ascomycota (Sac Fungi)

The largest fungal phylum, with over 64,000 described species. They produce spores inside microscopic sac-shaped structures called asci. This group includes morels, truffles, yeasts, many molds (including Penicillium), and most lichens (which are symbiotic partnerships between fungi and algae or cyanobacteria).

The ascomycetes are probably the most economically important fungal group. Baker’s yeast (Saccharomyces cerevisiae) is an ascomycete, as is brewer’s yeast. The mold that produces penicillin (Penicillium chrysogenum) is an ascomycete. Many plant pathogens — Dutch elm disease, ergot of rye, powdery mildews — are ascomycetes.

Basidiomycota (Club Fungi)

This phylum includes most of the organisms people think of as “mushrooms” — the ones with caps, stems, and gills. But it also includes puffballs, bracket fungi, rusts, smuts, and jelly fungi. About 32,000 species are described.

Basidiomycetes produce spores on club-shaped structures called basidia, typically located on the gills or pores under a mushroom cap. Many of the fungi involved in mycorrhizal networks are basidiomycetes.

Zygomycota, Chytridiomycota, and Others

Several smaller phyla round out the fungal kingdom. Zygomycetes include common bread mold (Rhizopus stolonifer). Chytrids are the only fungi that produce flagellated (swimming) spores, and they’ve gained notoriety for Batrachochytrium dendrobatidis, the chytrid fungus causing devastating amphibian declines worldwide — it’s driven multiple frog species to extinction.

Fungi and Medicine

The relationship between fungi and medicine runs deep — and it’s far from finished.

Antibiotics

Penicillin, discovered by Alexander Fleming in 1928 and developed into a usable drug by Howard Florey and Ernst Boris Chain in the 1940s, is arguably the most important medical discovery of the 20th century. It came from a mold — Penicillium notatum (later reclassified as P. rubens). Before penicillin, a simple scratch could become a fatal infection. After it, bacterial infections went from death sentences to treatable conditions.

Other fungal-derived antibiotics followed: cephalosporins (from Acremonium), griseofulvin (antifungal from Penicillium griseofulvum), and many more. About 45% of all antibiotics in clinical use have fungal origins.

Immunosuppressants

Cyclosporine, discovered in 1971 from the fungus Tolypocladium inflatum, enabled modern organ transplantation. Before cyclosporine, the body’s immune system would typically reject transplanted organs. Cyclosporine selectively suppresses the immune response, making kidney, heart, liver, and other organ transplants feasible. Millions of lives have been saved because a mycologist found a useful compound in soil fungus.

Statins

Lovastatin, the first commercially available statin drug (used to lower cholesterol), was derived from Aspergillus terreus. Statins are now among the most prescribed drugs in the world, taken by an estimated 200 million people globally.

Psilocybin Research

Psilocybin, the psychoactive compound in “magic mushrooms” (primarily Psilocybe species), has become the subject of intense clinical research. Studies at Johns Hopkins, NYU, Imperial College London, and other institutions have shown promising results for treatment-resistant depression, anxiety related to terminal illness, PTSD, and addiction. The FDA granted psilocybin “breakthrough therapy” designation for treatment-resistant depression in 2019.

This research has helped drive a broader cultural shift in how fungi are perceived — from feared or ignored organisms to subjects of genuine scientific and public interest.

Fungi and Food

Beyond the obvious — eating mushrooms directly — fungi are embedded throughout the human food system.

Fermentation. Yeast (Saccharomyces cerevisiae) makes bread rise, converts grape juice into wine, and turns barley malt into beer. Different yeast strains produce different flavors, which is why craft breweries obsess over their yeast cultures. Koji (Aspergillus oryzae) is essential to soy sauce, miso, sake, and many other Asian fermented foods.

Cheese. Molds give many cheeses their distinctive flavors and textures. Penicillium roqueforti creates the blue veins in Roquefort, Gorgonzola, and Stilton. Penicillium camemberti forms the white rind on Brie and Camembert. Cheese-making is, quite literally, controlled mold cultivation.

Mycoprotein. Quorn, a meat substitute made from Fusarium venenatum mycelium, has been commercially available since the 1980s. More recently, companies like Meati Foods and Nature’s Fynd are developing mycelium-based proteins as alternatives to conventional meat — growing fungal biomass in fermentation tanks and processing it into products with meat-like texture.

Mushroom cultivation itself is a major global industry. The worldwide mushroom market was valued at approximately $53 billion in 2024. China produces about 75% of the world’s cultivated mushrooms. Button mushrooms (Agaricus bisporus) dominate Western markets, while shiitake, oyster, enoki, and king trumpet mushrooms are increasingly popular.

Fungi and Environmental Solutions

Some of the most exciting modern applications of mycology involve environmental remediation and sustainable materials.

Mycoremediation

Certain fungi can break down pollutants that resist other forms of treatment. Paul Stamets, perhaps the most prominent public mycologist, has demonstrated that oyster mushrooms (Pleurotus ostreatus) can degrade diesel fuel, polycyclic aromatic hydrocarbons, and other petroleum-based contaminants in soil. White-rot fungi can break down some pesticides and even certain plastics.

The logic is straightforward: fungi evolved to decompose complex organic molecules (especially lignin, which is structurally challenging). Some synthetic pollutants are structurally similar enough that fungal enzymes can attack them too.

Mycelium Materials

Companies are using mycelium to grow packaging materials, construction insulation, acoustic panels, and even leather alternatives. Ecovative Design pioneered mycelium packaging as a replacement for polystyrene foam. The process involves growing mycelium on agricultural waste (like corn stalks) in molds — the mycelium binds the substrate into a solid, lightweight material that’s completely biodegradable.

Mycelium-based leather (marketed under names like Mylo and Reishi) is being adopted by fashion brands looking for sustainable alternatives to both animal leather and petroleum-based synthetics. Bolt Threads’ Mylo material has been used by Stella McCartney and Adidas.

Carbon Cycling

Mycorrhizal fungi transfer significant amounts of carbon from the atmosphere (via plant photosynthesis) into the soil. Research published in 2023 estimated that mycorrhizal fungi receive about 13 gigatons of CO2 equivalent per year from plants — roughly 36% of annual fossil fuel emissions. Understanding and potentially enhancing this process could contribute to climate change mitigation, though the science is still developing.

Threats to Fungal Diversity

Despite their importance, fungi face serious conservation challenges. Habitat loss, pollution, climate change, and overexploitation all threaten fungal diversity. Yet fungi are dramatically underrepresented in conservation policies.

Of the estimated 2.2-3.8 million fungal species, only about 600 have been evaluated for the IUCN Red List. Compare that to birds (over 11,000 species evaluated) or mammals (over 6,000). Fungi are, as some mycologists put it, the “orphans of conservation.”

This is changing slowly. In 2018, the Kew Royal Botanic Gardens’ State of the World’s Fungi report highlighted the need for fungal conservation. Several countries have begun including fungi in their biodiversity protection frameworks. But awareness and funding lag far behind what plants and animals receive.

How to Get Into Mycology

Mycology is unusually accessible for a scientific field. You don’t need a lab to start.

Foraging and identification. Joining a local mycological society (most regions have one) and going on group forays is the classic entry point. Learning to identify mushrooms in the field — examining spore prints, gill attachment, cap texture, habitat associations — develops observational skills that are genuinely useful.

A word of caution: some mushrooms are deadly. Amanita phalloides (the death cap) and Amanita ocreata (the destroying angel) can cause fatal liver failure from a single meal, and they can look similar to edible species to inexperienced eyes. Never eat a wild mushroom unless you’re absolutely certain of the identification. “When in doubt, throw it out” is the golden rule.

Citizen science. Platforms like iNaturalist allow anyone with a smartphone to photograph fungi, upload observations, and get identifications from experts. The Mushroom Observer website is specifically dedicated to fungal observations. These platforms contribute genuinely useful data to scientific research.

Growing mushrooms. Home mushroom cultivation — starting with oyster mushrooms, which are forgiving and fast-growing — provides hands-on understanding of fungal biology. Kits are widely available for $20-30, and the process of watching mycelium colonize a substrate and produce fruiting bodies is frankly mesmerizing.

Formal study. For those pursuing mycology professionally, relevant degrees include biology, microbiology, ecology, and botany (many botany departments include mycology). Graduate programs focused specifically on mycology exist but are relatively few — most mycologists train within broader biology programs.

Key Takeaways

Mycology is the study of fungi, a kingdom of life that’s more diverse, more important, and less understood than most people realize. Fungi recycle the planet’s dead matter, enable most plants to survive, produce life-saving medicines, make some of our best foods possible, and offer solutions to environmental problems from pollution cleanup to sustainable materials.

We’ve described about 150,000 species, but millions more likely exist undiscovered. The field is experiencing a genuine renaissance driven by molecular tools, environmental awareness, medical research on compounds like psilocybin, and growing public fascination with the fungal world.

Whether you’re interested in the science, the food, the medicine, or simply the weird and wonderful diversity of organisms that are neither plant nor animal, mycology rewards attention. The more you learn about fungi, the more you realize they’re not a strange footnote to biology — they’re one of its central chapters.

Frequently Asked Questions

What is the difference between mycology and botany?

Mycology studies fungi, while botany studies plants. Although fungi were historically classified as plants, they're actually more closely related to animals. Fungi can't photosynthesize, have cell walls made of chitin (not cellulose), and obtain nutrients by absorbing them from their environment rather than producing their own food.

How many species of fungi exist?

Scientists have described approximately 150,000 fungal species, but estimates suggest there are between 2.2 and 3.8 million total species. That means roughly 90-95% of all fungal species remain undiscovered and unnamed, making mycology one of the most exploration-rich fields in biology.

Are all mushrooms fungi?

Yes, all mushrooms are fungi, but not all fungi are mushrooms. Mushrooms are just the visible fruiting bodies (reproductive structures) of certain fungal species. Many fungi — including yeasts, molds, and many parasitic species — never produce mushrooms at all.

Can studying mycology lead to a career?

Yes. Mycologists work in pharmaceutical research, agriculture, environmental remediation, food science, forestry, medical diagnostics, biotechnology, and academia. The growing interest in fungal-based materials, myco-remediation, and medicinal mushrooms has expanded career opportunities significantly.

What is the largest living organism on Earth?

A honey fungus (Armillaria ostoyae) in Oregon's Malheur National Forest. It covers approximately 2,385 acres (965 hectares), is estimated to be 2,400 to 8,650 years old, and most of its mass is underground in the form of root-like mycelial networks.