Write The Nature Of Fungi

Fungi Are Just Weird Enough To Make You Stare

I spent three years working in a lab that did fungal taxonomy, mostly on basidiomycetes. Not because I love mushrooms. Because someone had to ID them so the forest pathology people could figure out what was killing spruce trees. The work was tedious, poorly funded, and occasionally fascinating in the way a damp basement is fascinating. If you want to understand what fungi actually are, the short answer is that they are not plants, not animals, and not particularly easy to classify if you care about molecular phylogeny. They are their own kingdom, Opisthokonta-sister to animals, and they share more DNA with you than with an oak tree. That fact alone destroys half the things mycologists argued about in the 1990s.

Write The Nature Of Fungi

When I was writing up identification keys for a regional field guide, the section I kept coming back to was the one about lichenized versus non-lichenized species. Beginners mix them up constantly. A lichen is not a single organism. It is a partnership between a fungus and a photobiont, usually a green alga or cyanobacterium. The fungus provides structure. The photobiont provides carbohydrates through photosynthesis. Neither one survives alone in that form. I learned this the hard way when I submitted a manuscript describing what I thought was a new Cladonia species, only to have the reviewer point out that the thallus I had been examining was actually an epibiotic algal mat growing over the apothecia. The fungus was Cladonia rangei, well known. The algae was a nuisance I had not considered. It took me six weeks to rewrite the paper and apologize to the journal editor.

What Fungi Actually Do

Fungal cells have chitin in their walls, unlike plants which use cellulose. Their mode of nutrition is absorptive heterotrophy, meaning they secrete enzymes into their environment and absorb the broken-down molecules. This is fundamentally different from animal digestion, which happens intracellularly after ingestion. Fungi eat from the outside in, basically. The hyphal network, the mycelium, is the main vegetative body. Most of the visible mushroom is just a reproductive structure, a short-lived spore dispersal organ. The actual organism can be enormous and centuries old. There are documented Armillaria colonies in Oregon covering over a thousand acres and estimated to be thousands of years old. That is one individual.

Why Your Garden Soil Is Not What You Think

Mycorrhizal fungi form symbiotic relationships with plant roots. Arbuscular mycorrhizae, the Glomeromycota, penetrate root cortical cells and form structures called arbuscles where nutrient exchange happens. Ectomycorrhizal fungi form a sheath around the root and a Hartig net between cortical cells without penetrating the cell walls. Both systems improve phosphorus and nitrogen uptake for the plant. The plant provides sugars. It is a trade, not charity. I once spent two months trying to grow a specific ectomycorrhizal fungus in pure culture. It did not work. Some basidiomycetes, particularly many boletes and truffles, have not been successfully cultured axenically outside of symbiotic association. You can sequence them, you can describe them morphologically, but you cannot grow them on agar without their host plant's exudates or specific bacterial partners. This is a real bottleneck in fungal research and one that frustrates everyone who works in applied mycology.

Decomposers, Pathogens, and the Things in Between

Saprotrophic fungi decompose organic matter. They are essential. Without them, carbon would remain locked in dead wood and leaf litter indefinitely. The lignin-degrading white rot fungi, primarily Basidiomycota like Trametes and Phanerochaete, produce lignin peroxidase, manganese peroxidase, and laccase. These enzymes break down lignin, the complex polymer that makes wood rigid. Brown rot fungi take a different approach, degrading cellulose and hemicellulose while leaving lignin largely modified but intact. Pathogenic fungi are another category. Some are obligate parasites, meaning they require a living host. Puccinia rusts are good examples. Others are opportunistic, attacking stressed or immunocompromised hosts. Candida albicans is a human pathogen that is also a commensal. It lives on your mucous membranes harmlessly until something disrupts the balance, then it becomes invasive. The same organism, different outcome depending on context. I worked on a project where we tried to distinguish between saprotrophic and parasitic life histories in a group of Nectria-like fungi. The problem is that many species can do both depending on conditions. What looks like a pathogen on a wounded branch might just be a saprotroph colonizing dead tissue. Molecular tools helped, but even DNA sequencing cannot always resolve whether a fungus is killing a host or just cleaning it up.

Edible And Poisonous, With A Gray Area You Should Respect

The most dangerous misconception about wild mushrooms is the false certainty people have about identification. There are simple rules people repeat online: brown spores mean edible, milky latex means Lactarius, gills that turn black mean ink caps. These heuristics fail. Regularly.. Galerina marginata contains amatoxins, the same cytotoxins found in Death Cap (Amanita phalloides). It grows on wood, has a ring, brown spores, and looks superficially like several edible mycena or conocybe species. A single mushroom can kill an adult. It fruits in autumn under conifers across much of the Northern Hemisphere. People pick it every year. I have held specimens that looked identical to edible varieties under field conditions. Spectroscopy and DNA barcoding are the only reliable methods for definitive identification in ambiguous cases. Field guides are helpful but insufficient for anything beyond the most obvious species. If you forage, learn five species perfectly instead of fifty poorly. The ones you learn well will keep you alive longer than the ones you guess at.

The Hidden World Under Your Feet

Fungal biomass on Earth is estimated at around 120 gigatons of carbon. That is more than the biomass of all animals combined and roughly comparable to all plants. Most of this biomass is underground, in soil and root systems, invisible and unmonitored. We know less about soil fungal communities than we do about deep-sea fish, partly because they are harder to access and partly because funding follows charisma. Environmental DNA sampling has changed this. Soil metabarcoding using ITS region primers can profile fungal communities in a single sample in a few days. Ten years ago this took months of culturing and morphological examination, and you missed everything that would not grow on your plates. The data quality is different, too. Culture-based methods bias heavily toward fast-growing copiotrophs. Environmentally derived sequences capture the slow-growing oligotrophs and the symbionts that dominate most ecosystems. I switched from culture-based to sequence-based methods around 2018. The learning curve was steep. Primer choice matters enormously. The ITS region has variable copies per genome, which complicates abundance estimates. Some taxa amplify poorly with standard primers. You need negative controls, you need to account for PCR bias, and you need to understand that relative abundance in sequencing data is not the same as absolute biomass. None of this is difficult, but it is easy to mess up if you treat fungal eDNA like bacterial 16S work and assume the same rules apply.

What Fungi Tell Us About Evolution

The transition from water to land involved fungi before plants did. Fossil evidence suggests fungal-like organisms were involved in early soil formation, breaking down rock and contributing to the primordial substrate that land plants would eventually colonize. The symbiotic relationship between fungi and early plants, likely similar to modern arbuscular mycorrhizae, is probably what allowed plants to establish on terrestrial habitats in the first place. Glomeromycota, the arbuscular mycorrhizal fungi, have not been observed undergoing sexual reproduction in the laboratory. Their life cycle appears to be primarily asexual, with multinucleate spores containing genetically distinct nuclei. Whether they have a cryptic sexual phase or are ancient asexuals is debated. Either way, they have persisted for over 400 million years, which is a successful strategy even if it puzzles evolutionary biologists who expect sex to be universal. Horizontal gene transfer between fungi and plants is documented, though rare. More commonly, fungi share genes with bacteria in soil through transposon-mediated mechanisms. The ecological significance of these transfers is unclear, but they complicate any simple tree of life model. Fungal phylogenies built from single genes do not always match species trees, and whole-genome analyses are starting to reveal complex patterns of reticulate evolution that classical taxonomy struggles to represent.

Practical Mycology: Things That Work And Things That Do Not

If you are starting with fungal identification, get a decent microscope. A compound scope at 400x minimum will let you see spore morphology, which is the single most useful character in fungal taxonomy. Hand sections of basidiocarps mounted in aqueous calcofluor white will fluoresce under UV, making cell wall structures visible without complex staining. This costs about forty dollars and transforms your ability to differentiate species that look identical macroscopically. Spore prints are useful but limited. Color is a broad classifier. In Agaricus, spore color goes from white to pink to brown to black, and each range contains dozens of species. Within the brown-spored group, you need gill attachment, ring morphology, bulb shape, and molecular data to go further. Don't stop at the spore print. For cultivation, pasteurized substrate works for many common species. Pleurotus oyster mushrooms grow on straw that has been heat-treated at 80°C for two hours. The pasteurization kills competing organisms without sterilizing completely, which actually helps because residual bacteria can inhibit some contaminant molds. Full sterilization at 121°C is necessary for Psilocybe on grain but overkill for oysters and often increases the risk of Trichoderma contamination because the substrate becomes a blank canvas with no microbial competition at all.

I have seen people lose entire runs to Trichoderma because they assumed clean technique was enough. It is not. Spores are everywhere. Trichoderma grows faster than almost any cultivated fungus and produces antibiotics that suppress competitors. The solution is not heroic sanitation but rather managing the ecology of your substrate. Slightly competing microbiota, proper moisture, and temperature selection that favors your cultivar over typical contaminants will prevent most problems without requiring a laminar flow hood.

The Economic Side Nobody Talks About

Fungi generate revenue through mushrooms, yes, but also through enzymes, antibiotics, and fermented products. Aspergillus species produce amylases and proteases used in detergent and food processing. Cyclosporine, an immunosuppressant discovered from Tolypocladium inflatum, revolutionized organ transplantation. Statins came from Aspergillus terreus. These are not historical curiosities. The pharmaceutical industry continues to mine fungal natural products, though high-throughput screening has reduced the discovery rate compared to the golden age of the 1950s and 1960s. The mycotoxin problem is economic as well as biological. Aspergillus flavus and A. parasiticus produce aflatoxins in stored grain and nuts. Aflatoxin B1 is one of the most potent carcinogens known, and regulatory limits in food are measured in parts per billion. Farmers in subtropical regions lose significant portions of their harvest to these contaminants annually. There is no easy fix because the fungi are endemic in the soil and infect crops under warm, humid conditions that are increasing with climate change. Biocontrol strategies using non-toxigenic strains of A. flavus to outcompete toxic strains have shown promise in cotton boll and peanut systems. This biocontrol approach, sometimes called atoxigenic strain replacement, reduces aflatoxin contamination without pesticides. It is not a complete solution, and effectiveness varies by environment, but it is one of the few fungal applications that scale to agricultural production without prohibitive cost.

Where Mycology Is Heading

The fungal tree of life is still being revised. New phyla and classes are described regularly, particularly among the Microsporidia and cryptic lineages recovered from environmental sequences. The relationship between Cryptomycota and other fungal groups remains unresolved. Some researchers argue they should be placed within Zoopagomycota. Others see them as a separate lineage. The data are incomplete, and the phylogenetic signal is weak for several key nodes. Genomic sequencing is accelerating taxonomic revision. Species that were considered monomorphic based on morphology are turning out to be complexes of cryptic species separated by small morphological differences and large genetic distances. Fusarium is a well-known example, where what was once classified as a handful of species is now dozens, many indistinguishable without PCR or sequencing. Citizen science is expanding fungal distribution data rapidly. Platforms like iNaturalist and Mushroom Observer have generated millions of observations, much of it georeferenced and timestamped. This data is imperfect, heavily biased toward charismatic species and populated areas, but it is far better than the sparse herbarium records it supplements. Researchers are beginning to use these datasets for biogeographic and phenological studies that were impossible fifteen years ago.

I have spent more time than I care to admit arguing with people who think fungi are either glorified plants or interesting curiosities. They are neither. They are a distinct lineage with unique biology, enormous ecological importance, and practical applications that affect everything from agriculture to medicine to materials science. Understanding them requires letting go of plant analogies and accepting that their world operates on different rules, chemically and ecologically. That shift in perspective is the hardest part and also the most rewarding once it clicks.