The Huge Impact of Mycorrhizal Colonization on Plant and Soil Health

By Paul Reed Hepperly, David Douds & Mike Amaranthus.

Leonardo da Vinci remarked, “in order to be a successful farmer one must know the nature of the soil.” Even today in the age of hydroponics, most of our food, over 98 percent by some estimates, is grown from field on a soil medium. Beyond growing our food, the way we treat our soil determines the nature of our environment and the climate.

There is a great and still relatively undeveloped agronomic and environmental opportunity that could make an important global difference. This opportunity is hidden underneath our feet, in the living soil. The soil is home to the most populous community on the planet. Around the seven continents, the living soil is the Earth’s most valuable bio-system, providing ecosystem services worth trillions of dollars. The most limiting resource for global food system is drought, with over 75 percent of the crop insurance outlay related to these events.

The vast majority of our cultivated soils are in an eroded and degraded state. As we increase demands on our soil to feed billions, we are losing it and depleting it at an unprecedented rate. Our ability to transform it will address both of these key issues. In addition to addressing drought and climate, the web of soil life is critical to maintaining and building soil resources we need now and into the foreseeable future.

Mycorrhizal inoculation effects
This University of Florida photo shows the effect of mycorrhizal inoculation on maize drought response. Mycorrhizal colonization (front left and back right) helps plants avoid severe drought losses compared to the control (front right and back left). Note how the extension of the mycorrhizal effect expands into the adjacent plot showing the spreading nature of mycorrhizal hyphae feeding the adjacent plants with both water and nutrients.

Elaine Ingham emphasized the concept of the soil food web. In the living soil food web the keystone species of the living soil community are mycorrhizal fungi. These unsung heroes cannot be cultured apart of plant roots. Mycorrhizal fungi are obligate symbionts growing from the soil into the plant roots.

About 80-90 percent of all land plants depend on these fungi for the procurement of water and nutrients. The fungal network represents a massive “web” of opportunity. When optimized, the multiplication of soil/root interfaces increases by several magnitudes via mycorrhizal colonization.

Mycorrhizal Importance

Scientists suggest mycorrhizal evolution appeared over 460 million years ago, coinciding with land plant development. Mycorrhizae are viewed as an evolutionary advancement that allowed plants on land to survive on periodically dry and hostile land surfaces.

roots with mycorrhizal fungi
When roots are colonized with mycorrhizal fungi they exude the sticky sugary protein glomalin that promotes the adherence of soil particles together. The mycorrhizal root above is coated with glomalin and causes the sand to stick rather than slough off.

Researchers suggest that less than 1 of 20 soil microorganisms have ever been identified and cultured. Considering this startling statistic, soil microbiology still represents a largely unchartered and vast frontier filled with promise and potential that could make a significant difference to agriculture.

The traditional underestimation of mycorrhizal importance may partly be based on unfamiliarity since most scientists have little knowledge, experience or appreciation for these microscopic underground denizens. Even many mycologists are not well versed on this topic. Beyond the scientific community, farmers, extension specialists and public policymakers are even more in the dark.

Soil Erosion Control

While the development of topsoil is considered a slow process, losses of topsoil by erosion can be rapid and vast. Erosion can easily overrun the natural capacity of soil genesis. While erosion has been viewed as a physical process, everything in the soil is affected by the life within it. For example, sticky mycorrhizal filaments create an organic glue that binds soil into stable aggregates that resist detachment, erosion and rapidly move water into the soil profile, preventing overland flow of soil.

When roots are colonized with mycorrhizal fungi they exude the sticky sugary protein glomalin promotes the adherence of soil particles together. Since mycorrhizae can form with so many of our important crop species, could these microscopic organisms reverse the effects of soil deterioration? If they can, then how do they do it?

There are copious citations showing how the loss of topsoil and the decay of soil organic matter can lead to a degradation of our land resources. The disappearance of soil organic matter under modern cultivation practices gives a typical bathtub-shaped disappearance curve where initiation of continuous cultivation gives a rapid plummeting of the soil organic matter which then reaches a degraded equilibrium value less than one half of the original value.

In 1876 the Morrow plots of the University of Illinois were started. There rotations demonstrate this bathtub disappearance of soil organic matter related to modern farming techniques. The results were similar to results in Sanford plots of University of Missouri and Macgruder plots of Oklahoma State University as well as studies from other major land grant universities. In practice the potential of loss of productivity is particularly associated with maize monoculture that dominates the modern North American landscape.

Dust clouds during great depression
Giant dust clouds common during Great Depression during droughts in the Plains region.

During the 1930s in the United States the Great Depression coincided with massive soil erosion known as the Great Dust bowl era. In order to address this massive soil loss, soil conservation methods were marshaled through Soil Conservation Service of the U.S. Department of Agriculture under President Franklin Delano Roosevelt and Agriculture Secretary Henry Wallace.

Differing Outcomes From Synthetic Input and Organic Agriculture Systems

Since the end of World War II, the high productivity of agriculture has focused on intensive use of cultivation, synthetic fertilizers, monocultural production methods and intensive use of pesticides. These methods were also degrading mycorrhizal populations important for stabilizing surface soils from wind and water erosion.

Methods that were traditionally employed for maintaining and building biological robust soils were not a prime consideration. These practices included organic manuring, rotations and employment of forage and haying in rotations that employed mixed crop and animal systems of production.

In 1978 The Rodale Institute started the Farming Systems Trial (FST) that directly compares a biological input approach exemplified by organic agricultural systems compared to a typical synthetic input approach. The conventional approach used a maize and soybean crop rotation with full input packages, i.e. synthetic fertilizers and pesticides. The biological input approach used a more extended crop rotation with cover crops and a focus on legume crops and cover cropping that has been shown to promote mycorrhizal populations.

While the short-term effects of synthetic fertilizers on crops can be rapid and spectacular the long-term effects of these may be quite different. When nitrogen is applied to legumes the result is atrophy of the natural fixation of nitrogen by bacteria. Likewise when synthetic phosphorus is applied in abundance to the seed zones of crops it can trigger the plant not to accept the mycorrhizal fungi that mobilize soil phosphorus.

Because biological inputs take time to accumulate in the form soil organic matter, maize yields were only fully competitive with synthetic approaches until the fourth year of the FST. After that time, the yield in drought years was consistently superior with biological approaches compared to conventional maize and soybean control systems. These results are the cumulative effect of soil improvement that Robert Rodale coined as soil regeneration.

System analysis has clearly demonstrated that not only does the biological input approach produce highly competitive crop yields over time, but also soil carbon and nitrogen values increase significantly. The FST puts the soil organic matter disappearance curve on its head, leading to a soil organic matter accrual curve. This is only appreciated under a long-term experimental vista.

Mycorrhizal Fungi and Glomalin

In 1996 Sara F. Wright of USDA-ARS began publishing scientific articles on the ability of mycorrhizal fungi to capture soil carbon, suggesting fully one-third of the carbon in soil is related to these organisms. Dr. Wright and her collaborators showed the profound effect of the sugary organic glue, glomalin, excreted from mycorrhizal fungi as a key for aggregating or clumping soil.

As the sticky glycoprotein glomalin increases in the soil so does the size and persistence of soil aggregates. Persistent large aggregates reduce the ability of small soil particles to be dislodged by wind and water.

Rodale Institute Farming Systems Trial Results
In 1978 The Rodale Institute started the Farming Systems Trial (FST) that directly compares a biological input approach exemplified by organic agricultural systems compared to a typical synthetic input approach.

Studies at Rodale Institute show that biological inputs including rotation, cover cropping and organic amendments can be highly stimulative to mycorrhizal diversity and activity. Using Paspalum notatum flugge, a bay grass, mycorrhizal fungi were effectively propagated to provide the ability to artificially inoculate and enhance mycorrhizal activities with positive results for crops such as potato and strawberries in multiple-year trials.

We see the great potential of utilizing mycorrhizal fungi and organic amendments for their symbiotic and synergistic effects, and we see gradual appreciation and adoption by the agricultural community.

Some scientists express a valid concern about the exact nature of glomalin, citing need for better knowledge it mode of action. We concur with this need for additional information, and we also see its potential in critical issues pressing in our future. In a warming world, soil organic matter resources are needed more than ever.

In addition, agriculture issues related to water quality and global greenhouse gas emissions are addressed by putting soil organic matter in a positive trajectory. One of the biggest potentials to counteract these degradation issues may well be grounded in a sticky fungus that can be re-established and preserved in modern agricultural systems.

How Mycorrhizal Fungi Help Plants Deal with the Stress of Climate Change

Myccorrhizal fungi extend beyond plant roots
The massive capacity of mycorrhizal fungi (white threads) to extend beyond the much more limited plant root system (brown).

In March, the United Nations Intergovernmental Panel on Climate Change pointed to melting ice caps and rising sea levels, stressed water supplies, heat waves and erratic weather, with a stern warning about the danger to global food supply.

Food demand is rising 14 percent every decade, while there is tremendous need to reduce the environmental impact of agriculture. By 2030 our planet is expected to support 8.3 billion people. The United Nations Food and Agriculture Organization has stated that by then farmers will have to produce 30 percent more grain than they do now to keep pace with demand.

The UN Panel points to serious risk of major disruption to social stability due to coming climate change, drought and food shortages. Historically, we have seen how drought induces a cascade of changes, disrupting agriculture, trade and social cohesion.

In the American Southwest in the 12th century, the people known as the Anasazi reached their cultural peak and then collapsed because of drought. Most recently, increased food prices and water shortages were a major contributing cause to the unrest that led to the Arab Spring, particularly to unrest in Syria.

Closer to home, we saw a devastating drought in California with its massive impact on agriculture in a state that grows half the nation’s fruits and vegetables. The year 2013 was the driest in California’s recorded history.

Agriculture needs to use resources more efficiently. We need to produce more food per unit of water, energy and fertilizer. Few people comprehend how much water is needed to grow food. On average it takes 1 liter of irrigation water to grow 1 calorie of food. Consider the average American consumes in excess of 3,000 calories a day and you can grasp the enormity of water necessary to sustain the population here in the United States.

The UN Panel suggests many steps to adapt to a changing climate. They suggest that farmers could breed new species to better resist heat and drought. Drip irrigation, (where water is applied directly to the plant’s base) reduces water use compared to overhead spray applications. Mulching the soil surface and no till agricultural systems retain water in the soil. Reducing water loss from irrigation systems and evaporation from canal and reservoirs could also help. Better water harvesting techniques could be used to collect and disperse water to crops.

In a world of increasingly volatile weather and depleted soils, water has become a precious resource. There are some places on Earth where a barrel of water costs more than a barrel of oil. No one understands this better than farmers, especially today with severe drought events seeming to become the norm. Yet we often see abundant, verdant vegetation in natural ecosystems without the benefit of irrigation. How do natural areas provide for such luxuriant plant growth without irrigation?

One key factor is a partnership between mycorrhizal fungi and plants. Fungal filaments extend into the soil and help the plant by gathering water and nutrients and transporting these materials back to the roots. Plants that have mycorrhizal fungi growing on their roots survive better after transplantation and grow faster. The fungal symbiont receives shelter and food from the plant, which in turn acquires an array of benefits such as improved uptake of water, drought and salt tolerance, and an overall increase in plant growth and development.

Grass with mycorrhizal fungi withstands drought
Mycorrhizal fungi above produced on bay grass P. notatum flugge. The effects of these fungi were particularly notable under periodic drought common in rain-fed agriculture.

Mycorrhizal plants show higher tolerance to drought. Like a sponge, they absorb water during moist periods and retain and slowly release it to the plant during periods of drought. Plant systems in natural areas generally achieve levels of drought tolerance far exceeding those found in agriculture partly due to the enormous web of mycorrhizal hyphae and specialized storage cells which protect the plant communities from extreme soil moisture deficits.

As research shows, mycorrhizae help plants become more drought-tolerant due to effects on soil structure and improved plant nutrition. In addition, the hyphae of the fungi allow access to soil pores of very small diameter that retain both water and nutrients as soil dries. Mycorrhizal fungi can act as a kind of drought insurance as farmers struggle with the effects of a less predictable, changing climate.

Degraded lands are more likely to experience significant drought impacts. Populations of soil microbes are lost when the land is cleared and intensively tilled. Soil fumigation, fungicide use, cultivation, compaction, soil erosion and periods of fallow are factors that can adversely affect populations of beneficial soil organisms and soil organic matter.  These influences compromise the ability of the soil to store water and release it to plants.

Soil and carbon losses are the root of many soil degradation issues and the intensive use of some chemical fertilizers and pesticides have caused tremendous harm to the environment and life in the soil. Part of our strategy to combat this degradation is to re-establish beneficial life in the soil using biological inoculants.

Biological inoculants contain organisms that enrich the nutrient and water-holding capacity of soil. Bio-fertilizers and bio-inoculants are the fastest growing sector of agricultural research and technology because they increase yields for many important crop species. They represent a step we can take now to begin to transition to a long-term sustainable system based on healthy living soils.

For millions of years the powerful combination of organic amendments and soil biology has demonstrated its success, and today we are beginning to see these benefits on large-scale farming. In North America both large-scale conventional and organic farmers are applying mycorrhizal fungi to wheat, corn, soybean, alfalfa and vegetables. Many will also use other organic amendments to stimulate their soils with beneficial biology, improving water retention and uptake.

In India, Europe and South America, farmers are using mycorrhizal inoculation to decrease their inputs and increase yields. In America several large seed companies utilize a “smart seed” mix and inoculate millions of pounds of seeds annually with mycorrhizal fungi to increase the plants’ drought tolerance.

Our work suggests in the roots of our crops and their fungal extension are critical to keeping our soil resources from being washed and blown away. Biological and organic matter inputs will allow a more productive agriculture future while simultaneously reducing the need for inputs that have known side effects on our soil and its biological capacity.

Healthy soil hosts a complex of microscopic life-forms engaged in living, dining, reproducing, working, building, moving, policing, fighting and dying; all these activities help the crop plants that feed them. Perhaps the most important activity the living soil provides for plants is storing, accessing and absorbing water and nutrients.

The living soil is the ultimate source of our health. It is also a fundamental source of our security and social well-being. The living soil and mycorrhizal fungi are not a silver bullet that will solve all the world’s problems, however, starting underfoot can make a difference and a healthier and safer world.

Editor’s Note: This article appeared in the May 2018 issue of Acres U.S.A.

Paul Hepperly is former Research Director Rodale Institute Kutztown, Pennsylvania; David Douds is former Research Microbiologist U.S. Department of Agriculture Res. Service, Wyndmoor, Pennsylvania. Mike Amaranthus is Associate Adjunct Professor Oregon State University and President of Myco Analytics LLC in Grants Pass, Oregon;


Al-Karaki, G.N. 1998. Benefit, cost and water-use efficiency of arbuscular mycorrhizal durum wheat grown under drought stress. Mycorrhiza 8:41-45.

Amaranthus, M.P. and J.M. Trappe 1993.  Effects of erosion on ecto-mycorrhizal and va-mycorrhizal  inoculum potential of soil in southwest Oregon. Plant and Soil. 150(1):41-49.

Amaranthus, M. 2008. Soil life and carbon. Acres U.S.A. 38(3): 5 pages.

Amico, J.D., A. Torrecillas, P. Rodrigiez, A. Morte and M.J. Sanchez-Blanco. 2002. Responses of tomato plants associated with the arbuscular mycorrhizal fungus Glomus clarum during drought and recovery. Journal of Agricultural Science 138:387-393.

Bethlenfalvay, G.J. M.S. Brown, R.N. Ames and R.S. Thomas. 1988. Effects of drought on host and endophyte development in mycorrhizal soybeans in relation to water use and phosphate uptake. Physiologia plantarum 72:565-571.

Borkowska, B. 2002. Growth and photosynthetic activity of micropropagated strawberry plants inoculated with endomycorrhizal fungi (AMF) and growing under drought stress. Acta Physiologiae Plantarum 24:365-370.

Comis, Don. 1997. Glomalin Soils Superglue. Agriculture Research. USDA Research Service 23.

Comis, Don. 2002. Glomalin, Hiding Place for a Third of the World’s Stored Soil Carbon. Agriculture Research September pages 4-7.

The Role of AM Fungi in Agricultural Ecosystems

By Dr. Wendy Taheri 

Today we are going to examine the role arbuscular mycorrhizal (AM) fungi play in providing phosphorus and other benefits to plants and the impact of chemical fertilizers on plant-fungi symbiosis.

Nutrient Cycles

hands holding soil

You often hear about the P-cycle (phosphorus) or the N-cycle (nitrogen) and have probably seen all sorts of graphics demonstrating how these nutrients move in the environment. I am going to focus on phosphorus (P) because it is generally the most limiting nutrient for plants. The reality however is that these cycles are interlinked and altering one cycle will impact other things. All plants need three basic macro-nutrients: N, P and K (nitrogen, phosphorus and potassium).

When you buy fertilizer those are the elements you look for. However when you saturate your agriculture system with these nutrients, carbon becomes the limiting factor, not to plants, but to the microbes in the soil that can serve as storage devices for nutrients, keeping them from leaching out of the system. Increases in P also lead to increases in utilization of other nutrients that are necessary for plant growth.

Because P is a highly reactive element it can occur as a constituent of many different kinds of molecules. This makes it very difficult to accurately measure, because testing methods tend to focus on a specific source of P, bound in a specific substrate. The two most commonly used methods for testing P in soil are the Bray and Olsen methods. The Bray method measures acid soluble forms of P bound mostly to aluminum and iron in the soil.

The Olsen test is used for more alkaline soils that typically contain a lot of calcium-bound phosphates. This method frees P from calcium carbonate and iron oxides and then measures the amount of P in solution.

Both the Bray and Olsen P tests target inorganic P (Pi). This is because plants can uptake Pi directly from the soil when it is dissolved in water; hence the effectiveness of phosphate fertilizers. Get enough P into solution at the right time and your plants get bigger. Pi, however, has a fleeting life in soil. It is quickly bound to other things, runs off, or leaches away. It leaves the system and exits the natural cycles that keep the phosphorus where you want it, which is within your field. If you run these tests on soil from natural ecosystems you will discover that there is very little inorganic phosphorus available. Yet these systems produce more plant biomass than our carefully cultivated and heavily fed cropping systems. How is this possible?

P is hoarded in natural ecosystems by living organisms. It’s a limiting nutrient so nearly every little bit is scavenged and incorporated into living cells. This system is highly efficient and leaves very little Pi lying around waiting to wash away and get lost from the system. This is the organic side of the equation, and our current testing methods tend to ignore organic phosphorus (Po). Why? Because plants can’t uptake Po directly. Organisms in the soil however, can make Po available to plants.

As those billions of microbes in a handful of soil go through their life cycles living and dying, they are providing a constant source of nutrients. Some bacteria mineralize Po, turning it into Pi, which makes it directly available to plants. Arbuscular mycorrhizal fungi are capable of passing both organic and inorganic forms of phosphate to plants. One of the huge differences between our cropland soils and natural ecosystems is the abundance of arbuscular mycorrhizal fungi. When I extract spores from cropland soil, most of what I see is literally black, dead or unhealthy looking spores. The extractions are starkly different than those from natural ecosystems, which are full of plump, brightly colored, healthy looking spores.

We found that 50 ml of soil (slightly less than 1/4 cup) from a remnant of native prairie contained over 1,300 AM fungal spores, while the same amount of cropland soil, from the same area, averaged fewer than 200 AM fungal spores (Figure1). Furthermore, non-AM fungal spores found in the extractions were the dominant fungi in agricultural soils, while they were a very small percentage of the spores found in native prairie soil (Figure 2). In agricultural soils there were nearly three times more non-AM fungal spores than there were AM fungal spores, while in native prairie soil AM fungal spore production outnumbered non-AM fungal spores by nearly five to one. This is a very important difference because non-AM fungi may compete with AM fungi for resources, while providing little or no benefit to crops.

What are we doing that is killing them?

Probably, the largest contributor to this situation is the application of inorganic phosphate fertilizers. When we saturate the soil with plant-available phosphate, plants reject their symbiotic partners. Under natural conditions, plants pay these fungi for phosphorus. They exchange sugars, which they can efficiently acquire through photosynthesis, to the AM fungi for harder to get phosphorus. Both organisms are specialized in this regard. When we provide a ton of phosphate, the plant rejects colonization. AM fungi are obligate symbionts. This means they cannot survive and reproduce without a host.

Deny them a host for very long and they soon begin to die. Eventually you have the situation we see in our croplands. But they are not all gone. So who are the survivors?

Those species that are the most highly infective have managed to hold on. With all that fertilizer in the soil, they don’t have to work very hard either. We are literally selecting for less beneficial microbes in our soil. But we don’t stop there. We also coat our seeds with both fungicides and other pesticides. In fact, it’s getting harder and harder to find uncoated seeds. Since most of the microorganisms in soil fall into the “good” category, this sort of indiscriminate poisoning is likely to kill more good things than bad things. If you are combating a specific problem in your field, you treat for it. Prophylactic treatments to protect seeds “just in case” are not only an invitation to resistance, but it kills things that you want living in your soil.

Let’s consider the shift in fungal populations from AM fungi to non-AM fungi. Try to imagine the root system of a plant as the streets in a gated community. The street is lined with houses. Each house represents a niche in an ecological community.

A niche is where something can live and flourish. A plant’s root system provides a home for a wide range of organisms. Now we apply a pesticide and suddenly a large percentage of those houses are empty. Nature abhors a void.

Something else is now going to move into those empty houses. Will you get a good neighbor or a bad neighbor in each of those houses? Well, that is something of a craps shoot — it just depends on what is nearby. Every time you go through a pesticide cycle, you roll the dice again.

Eventually, something you really don’t want is going to move in. This is yet another reason why pesticides should be used sparingly.

How do you beat the odds?

You choose management techniques that favor the most beneficial organisms.

Remember, every organism living in the soil is competing with every other organism for resources. If you throw the balance to favor the beneficial organisms their populations can increase. This means when chemical intervention is necessary the odds are better of getting a good neighbor after you wipe out half the neighborhood. It also means during periods when intervention is not required, what the neighborhood is full and there’s little room for something else to move in. You stack the deck in your favor. It is much easier to jump into an empty house than it is to try and evict the current resident — so fill those houses with good neighbors.

We’ve told you most of what’s in the soil falls into the good zone. However some things are better than others for your plants, and you can’t manage for everything when there are literally billions of organisms in the soil. You need to manage for the support of the most beneficial group of organisms for plants.

This group is undoubtedly the arbuscular mycorrhizal fungi. Don’t get me wrong, there are a host of bacteria and fungi out there that promote plant growth, but nothing out there has shown the diverse benefits and defense capabilities that arbuscular mycorrhizal fungi demonstrate overall. Furthermore, managing for them is unlikely to seriously threaten other beneficial organisms, unlike chemical applications.

So let’s talk about these mysterious organisms so few people have ever seen and take a realistic look at what they can do for plants.

Arbuscular Mycorrhizal Fungi

AM fungi are plant symbionts. Symbiotic organisms are generally interdependent upon one another. In the case of AM fungi and plants, it is an obligate relationship for the fungi. The degree of plant dependency upon these organisms varies widely and some plants are unable to live without them, while others are completely non-mycorrhizal and do not act as hosts for AM fungi. It is estimated that 80-90 percent of all flowering plants are mycorrhizal. Most of our crops fall into this group.

The mycorrhizal symbiosis is the oldest symbiosis known to science. Fossil evidence suggests plants first colonized land with the help of AM fungi. That means this intimate relationship has been evolving for over 400 million years. It is a biologically complex relationship that we don’t fully understand yet.

It begins when a seed germinates. The young plant produces hormones called strigolactones that attract AM fungi to it. The plant wants to be colonized. In fact, it prepares channels for the AM fungi that run between the cells in its roots. The fungi penetrate plant roots with a filament called a hyphae, and grow through these channels. Along the way it occasionally penetrates individual cells where it produces a structure called an arbuscule. The plant grows a special membrane to surround the arbuscule.

The interface between these structures is where nutrients and minerals are exchanged between plant and AM fungi. Once colonization has occurred, the fungus sends its hyphae into the soil. They are finer than the smallest roots and can penetrate pores in the soil that roots are too large to access, collecting water and nutrients which would otherwise be unavailable to the plant. Because the hyphae grow out from the plant’s roots, extending beyond them into the soil, they also extend the total volume of soil available to the plant for nutrient uptake.

Benefits of AM Fungi

First and foremost among the benefits of AM fungi is the uptake of phosphorus. Literally every species of AM fungi known provide this crucial service to plants. Phosphorus and sugar are the currency of this symbiosis. AM fungi are so specialized they can only feed on sugars obtained through their arbuscules.

If you try to grow them in a Petri dish with sugar in the agar, they germinate, go looking for a host and die when they don’t find one. They don’t start taking up sugar through their hyphae and growing independent of a host plant. This gives the plant a measure of control. It can dissolve arbuscules that are not providing phosphorus and deny the fungi carbohydrates.

However if the plant is not providing sugar, the fungi can stop providing phosphorus, or meter it out based upon how well the plant feeds it. Since both partners have control over metering an essential nutrient to the other partner, it becomes hard to cheat. This also demonstrates how saturating the system with phosphate fertilizer interferes with the relationship.

The plant suddenly no longer needs the AM fungi. And if that were the sum total of what AM fungi did, replacing them with chemical phosphate might be a good idea. However, AM fungi are complex organisms that do much more than just mine and meter phosphate.

Unfortunately for the fungi, the mechanism that regulates how plants respond to them depends on phosphate concentrations in the soil. Heavy applications of chemical phosphate destroy the symbiosis, and a host of other benefits are lost with it. These benefits include: drought tolerance, salt tolerance, improved plant nutrition, defense against pathogens including nematodes, improved soil quality and aggregation, tolerance to herbivory, increased fecundity (more seeds, fruits and flowers), reduced compaction stress, and reduced transplant shock. That is the short list, emphasizing only the benefits of particular interest to farmers and horticulturists.

Defending Your Home

If the plants are not strong and healthy they can’t afford the cost of supporting a population of AM fungi. The fungi want a healthy host — if their host dies they may also die. That plant is their home and they actively defend it against invaders. They don’t want to live in a derelict home, and they don’t want bad neighbors. Imagine the population of AM fungi populating your plant’s roots as a complex biological monitoring system. That fungus is making sure the plant has everything it needs.

It senses water stress, it provides more water. It senses a nutrient deficiency and it provides that nutrient. It senses nematodes approaching and it signals the plant to produce defensive chemicals. There is absolutely no product on the market available anywhere that can monitor every plant in your field and attempt to compensate for whatever stress factors the environment throws its way. Yet this is what AM fungi are doing for your plants every day, and we are killing them all off with our current and most common agricultural practices, the most basic of which is how we fertilize our fields. We have pushed so much Pi through our fields over the years that they are now rich in unavailable phosphorus. Remember much of the phosphate fertilizer we apply winds up bound to soil particles. Only something between 5-20 percent of the fertilizer you spent those hard earned dollars on, ever reaches your plants. However that untapped reserve of bound Pi and Po tied up in the microbial community and decomposing litter could be made available to plants through AM fungi.

The Conundrum

It has been demonstrated on average that AM fungi can replace up to 25 percent of the phosphorus we currently utilize without a decline in yield. However this generalization is not crop specific. Many experiments utilizing AM fungi depend on only a few easy to grow species that do well under greenhouse conditions.

Furthermore, these studies are often conducted in low P soils. If you suddenly stopped applying phosphate fertilizers to your fields, with a resident population of AM fungi that are now adapted to being highly infective and “lazy” (because they haven’t had to work hard with you providing the phosphorus) you would probably have trouble maintaining your yields. Natural ecosystems don’t rely upon 75 percent of the recommended amount of P. Theoretically, we should be able to replace most if not all of our P requirements with appropriate management techniques and restoration of AM fungal communities.

Transition studies in high P soils are needed to determine how long it will take for AM fungal populations to rebound, and to measure how effective those populations are at taking up phosphorus, and maintaining or increasing yields.

Editor’s Note: This article appeared in the September 2012 issue of Acres U.S.A. magazine.

Dr. Wendy Taheri is a mycorrhizal ecologist currently employed as a research microbiologist for the USDA Agricultural Research Service at the North Central Agricultural Research Laboratory in South Dakota. If you have specific questions about arbuscular mycorrhizal fungi, or about these articles, contact her at

Read more

Learn more about mycorrhizal fungi and its impact on soil health with this article, from the May 2018 issue of Acres U.S.A. magazine.

Read an interview with fungi guru and microbiologist/professional mycologist Trad Cotter here.

Interview: Fungi Guru Tradd Cotter Talks Mycoremediation, Mushroom Farming and Developing Research

Wild World of Mycology

Interviewed by Tracy Frisch

The field of mycology represents a  critical next frontier in biology. Relative to the plant and animal kingdoms, mushrooms have been largely neglected by science and yet they hold enormous promise for healing people and the planet, if you believe Tradd Cotter and others in his tribe. Fungi offer tremendously important applications in many realms of material life, from agriculture to medicine, from environmental cleanup to manufacturing and waste management.
Cotter calls it mycotopia.

In the new generation of passionate mycologists, Cotter stands out as a brilliant leader and restless innovator. He is a keen observer of and experimenter with all things mycological, an inveterate inventor who combines intuition and careful study with a wildly creative streak and is a much-in-demand lecturer who entertains and motivates while he educates. His first book, Organic Mushroom Farming and Mycoremediation has garnered outstanding reviews.

Cotter is a microbiologist, professional mycologist and organic gardener who has been tissue culturing, collecting native fungi in the Southeast and cultivating fungi both commercially and experimentally for more than 22 years. In 1996 he founded Mushroom Mountain, which he owns and operates with his wife, Olga. The company, his platform for exploring applications for mushrooms in various industries, currently maintains more than 200 species of fungi for food production, mycoremediation of environmental pollutants and natural alternatives to chemical pesticides. He’s particularly fond of coming up with low-tech and no-tech cultivation strategies so that anyone can grow mushrooms on just about anything, anywhere in the world. Mushroom Mountain is expanding to 42,000 square feet of laboratory and research space near Greenville, South Carolina, to accommodate commercial production, as well as mycoremediation projects. Tradd, Olga and their daughter, Heidi, live in Liberty, South Carolina, in the northwestern part of the state.

Tradd Cotter
Tradd Cotter

ACRES U.S.A. What has been the role of fungi in creating and maintaining a planet hospitable to human life and advancing civilization?

TRADD COTTER. Mushrooms are largely responsible for the colonization of land by plants. Historical evidence points to all organisms brewing in the primordial oceans, then evolving to adapt to terrestrial conditions, where fungi pushed ahead to lead the charge. They are one of the critical keystone groups that helped transform life on the planet into the diversity as we know it. Not many people know this, but fungi and animals share common ancestry, and primitive fungi were flagellated like spermatozoa until fungi lost their tails. Essentially what fungi do and have done is to repair devastated habitats. They create biodiversity and harmonize ecosystems. That’s a wonderful thing, especially in the last 200 years of the industrial age, when we’ve created a lot of problems that fungi have to solve.

ACRES U.S.A. You were talking about how fungi colonize microbial deserts.

COTTER. Yes, they do. Some of them are really good team players. They’ll collaborate and form interkingdom relationships. A lot of them form biofilms with bacteria, even in inhospitable conditions, in Arctic ice, permafrost or desert sands. They’re really good at unlocking nutrients and making things available for the next guy in line, kind of like relay race runners. They’re usually the sprinters, the first out of the gate. I call them first responders — they’re like EMS arriving at the scene, assessing the situation, patching up the people who are bleeding to death and then making amends.

ACRES U.S.A. Let’s consider some of the uses of fungi close to home. How can mushrooms fit into permaculture systems?

COTTER. Most modern agricultural systems are dead-end [rather than self-sustaining and cyclical]. Fungi can close the loop in permaculture systems. At our farm, we recycle just about everything with mushroom cultures, and we look for opportunities to create circular systems because that’s what nature does. It’s a no-brainer when you consider that nature knows no waste. Fungi take organic debris that no other organism on the planet can convert and make its nutrients bioavailable to the system. That’s a huge gift. Fungi can be used to create soil. They can unlock agricultural waste to create cellulose for biofuels like ethanol and butanol. They can be used in filtration systems in aquaponics and hydroponics. They can structurally bind together particles to help prevent erosion and slow runoff and keep soil where it’s supposed tobe. Of course, fungi also provide food. They’re a very low-fat, low-carb, high in protein by dry weight food source.

ACRES U.S.A. Describe how you can use fungi to create soil.

COTTER. A large percentage of a plant’s biomass is in the root system underground, so we have to take care of the roots. Fungi are good at breaking down things like wood chips, sticks, stalks and leaves. They disassemble all the organic debris that falls in the autumn. Fungi break down lignin and open up the cellulose and hemicellulose so bacteria and other soil-dwelling organisms can work on it. We’ve all seen bags full of leaves on the curb. One of the first things people could do is chip or shred them and leave them on-site to create soil. When we don’t do that, in a sense we’re the ones that are stripping away our topsoil in urban environments. I like to see people increasing their composting and creating more complex compost piles and then segueing into a larger scale. Thirty to 40 percent of household wastes are paper and cardboard, and the wastes from businesses can be 60 to 80 percent cardboard. These things can be composted with fungi to create soil.

ACRES U.S.A. What’s the relationship between worms and mycelium?

COTTER. I never thought I’d be a worm person, but I am. Everyone who is growing mushrooms has the capacity to vermicompost by default because fungi produce octanol, the chemical attractant for worms. It’s also what attracts slugs to beer. Mycelium in the garden or in a compost pile can vector a worm from over 10 feet away! That’s amazing, like being able to smell what’s cooking at home when you’re 20 miles away! Myceliated debris — the leaves or wood chips colonized by the mushroom mycelium — is one of their favorite food sources. If you colonize wood chips and leaves with fungi and produce edible mushrooms, an army of worms will come in right behind to eat the debris. Worm castings will be a byproduct.

Mycelium consuming creosote in a petri dish.
Mycelium consuming creosote in a petri dish.

ACRES U.S.A. Is it practical to grow mushrooms commercially or for home consumption without special equipment?

COTTER. Sure. The easiest mushroom to start with would be oyster mushrooms. That’s the training-wheel mushroom. It actually has twice the amount of protein, by dry-weight, as chicken or meat. There’s a lot of water weight, but taking account of their calorie content and rate of growth, mushrooms contain a lot of protein. Oyster mushrooms only take three to four weeks to fruit. To grow oyster mushrooms, you only have to be able to boil water to pasteurize your substrate. You submerge some straw or other agricultural waste in hot water for two hours and then pull it out, mix in spawn and stuff it in a plastic bag. There are other steps involved, but that’s the core of the work. You also need a place to grow mushrooms that maintains temperature and high humidity. You wouldn’t want to grow them in your house. You could create a little greenhouse or humidity tent. Their third requirement is oxygen. In a small, enclosed environment you can offset the carbon dioxide by growing microgreens, sprouts or other plants. This is where permaculture comes in. The plants convert the CO2 to oxygen, making it a closed-loop

ACRES U.S.A. This might be a good time to explain some fungal biology and how fungi differ from plants and animals.

COTTER. Fungi produce spores, though some plants do as well. A single gilled mushroom can produce millions of spores a day. A lot of mushrooms produce spores that can’t germinate on their own because they only have half the genetic information. So the majority of the spores that float out from a mushroom will end up single. They’ll never reproduce. Every now and then, two spores that are compatible will land close to each other. They’ll fuse genetic information so they have two nuclei in their cells. Then they’ll try to colonize a little part of their world with their mycelium. That’s the same thing as spawn, the white fluffy stuff that a beginner buys as a culture. What’s cool about mushrooms is that they try to take over as much territory as they can. Eventually they hit a barrier like the end of a log— and run out of food — or they run into another mushroom coming from the other direction. So they run out of food, and that’s when they fruit.

ACRES U.S.A. What do fungi eat, and how do they eat?

COTTER. That’s a great question. All mushrooms eat different things. They’re just like people. Some are picky eaters and some are not. Oyster mushrooms are omnivores. There’s a lot of leeway, which makes them good for a beginner. How a fungus eats is also interesting. They’ve been described as an animal turned inside out. A mushroom produces carbon dioxide — we talked about that. They also produce heat and sweat. As they colonize wood chips or straw that you pasteurized, they are actually sweating almost a microscopic puddle in front of them. It’s just enough to swim through, which is kind of cool.

ACRES U.S.A. Is that how they move?

COTTER. Yeah, they actually swim through their own sweat. They push and tunnel through. That’s how they can crawl across very dry environments. They essentially take humidity from the air or the growing substrate and absorb it. Then they sweat it out on their tips and swim through it. What’s in that sweat are chemical keys— their enzymes. That’s their stomach fluid, so they’re basically swimming through this soup of enzymes, which are out in front of them, unlocking nutrients and breaking down organic matter, like lignin in wood, into smaller molecules that they can absorb right through their body, which is their mycelium. They also excrete antibiotics into their sweat. They’re playing biological warfare with bacteria, announcing that this place is mine so back off. A lot is going on at that interface. Mushrooms are very opportunistic and territorial. Much like humans, they love to colonize and mine resources.

ACRES U.S.A. You talk about having gladiator matches.

COTTER. I set up a little arena for a mushroom and another organism to battle it out. I’ll put a fungus like a shiitake culture on one side and a bacterium like E. coli on another. Then I’ll ring a little doorbell, and walk away. When I come back 24 hours later, the fungus will have advanced, like a little army. It’s sweating metabolites, which are its biological weapons. The bacteria may be running away about an inch a day, which is like us running 22 miles per hour! When I give a talk, I say this is what I do on Friday nights. I don’t have cable, I have ’shroom TV. They have really helped me as a cultivator to understand the ecology of fungi, like how powerful they are in nature. A filament of fungal mycelium is 1 micron wide, yet they’re able to push their way through all their competitors.

ACRES U.S.A. It’s totally amazing. How did you discover the world of mushrooms?

COTTER. I wasn’t interested in fungi at all until I visited a mushroom farm. I was 20 years old and didn’t have a job. My mother told me about a mushroom farm on John’s Island where she worked so I went on a tour and got to see all these cool mushrooms growing. I was just blown away.

ACRES U.S.A. What were they growing there?

COTTER. Shiitakes, an edible medicinal, on little sawdust blocks. I’d never seen that before. A lot of people think mushrooms grow on manure, but this was super clean and looked space-age. It was cool, foggy and pleasant inside. I thought, “Hey, I want to work here!” Outside it was probably 100 degrees, dry and dusty. The owner gave me a pound of mushrooms and thanked me for stopping by. I jumped in my car and put it in first gear. Then I heard a loud bang. I couldn’t see anything, so I stopped and rolled down the window. The owner had run after my car and hit it to get my attention. He asked if I wanted a job. That was it.

ACRES U.S.A. What path were you on when the mushrooms grabbed you?

COTTER. It probably wasn’t a good one. I was in a band and living at home, and I think my mom and dad were probably like, please find something useful to do with your life. But this was just a job. I got paid $6 an hour. We were growing 1,000 pounds of shiitake mushrooms a week, and I started working 60-hour weeks. Then I got interested in wild mushrooms. I started collecting chanterelles because they were easy to identify and then chicken of the woods. The owner would pay me and sell them to chefs for top dollar. Then I would learn a couple more. I started to wonder what’s stopping us from growing wild mushrooms inside. I lived in a very small one-bedroom apartment with a tiny kitchenette and bathroom. I set up a little filter inside my bathroom and tried to culture wild mushrooms. I used Lysol and petri plates and jars and open flames. Lysol doesn’t mix with open flames.

ACRES U.S.A. It doesn’t mix with anything!

COTTER. I cloned my first wild mushroom, maitake, which is also called hen-of-the-woods. It was not cultivated at the time. I somehow got it to grow some mycelium and took it to work. On a Saturday when the owner wasn’t there, I ran the big sterilizing machine, which cost $50,000. I normally put shiitake cultures into the sterilized medium and made shiitake blocks. On that day, before I put the shiitake culture in, I bagged a few blanks and mixed my culture from home into them. Then I sealed them and stuck them in the colonization room without telling the owner. A month and a half later, all of a sudden I see baby maitakes growing out of these bags. The culture wasn’t pure by any means, but I lucked out. When the owner came in, I showed him. At first he was a little upset, but then he wanted to know how I did it. I was interested in making spawn, but he didn’t want to do any of that. I did convince him to start growing oyster mushrooms and we got very good at that, but we were still buying the spawn. Then we had an issue with the well water. He drilled a deeper well and ended up getting salt water pumped into the growing room. That shut the farm down overnight, and it was hard to recover. He gave the employees the option to stay. I decided to go, and then I started to buy laboratory gear and studied how to grow mushrooms. That week I wrote down the name ‘Mushroom Mountain.’ It seemed like a name that means big things.

ACRES U.S.A. What year was that?

COTTER. 1994.

ACRES U.S.A. Did you go to school to study mycology?

COTTER. No. I went to Clemson University for microbiology. I stopped going to school when the mushroom farm needed me 60 hours a week, so I put school on hold. Mushrooms were just way too interesting, and I thought I had a future in it. I went back to school years later. In between, I worked for landscape nurseries and retail nurseries in Hilton Head, and then I did landscape design privately to pay the bills. That led me down to West Palm Beach where I worked for the Henry Ford estate and Venus Williams. By chance I met my future wife Olga in Fort Lauderdale. Olga is from Croatia. I told her I was into growing mushrooms. That’s a strange pickup line. She said ‘that’s so cool because my family hunted mushrooms in Eastern Europe.’ It was something that we could do together, and we spent a lot of time in the woods. We were looking at how we could get out of Florida and put ourselves in a position to make this our livelihood. That’s when Mushroom Mountain came back out. We started building laboratory gear and found the place in the Carolinas where we are now. Then I ended up winning an EPA fellowship to go back to Clemson. It was like winning the lottery. The EPA paid for the rest of my school. During the summer of 2012 I did my fellowship. I told them I couldn’t accept the fellowship unless I could go to Athens, Georgia. They could have sent me anywhere in the United States or its territories.

ACRES U.S.A. Because it was close enough?

COTTER. It was an hour and a half away. On the weekend I would go home, and Olga and I would make spawn all weekend to keep our mushroom business going.

ACRES U.S.A. Let’s go to the work you’ve done in Haiti.

COTTER. Our work in Haiti came about after the earthquake occurred in 2010. World events affect me. My dad was in the Air Force, and we moved around. I lived in Syria and Egypt in ’80-81 when my dad was in the U.N. for a year. I’ve always had a soft spot for humanitarian disasters. We started experimenting with a different cultivation system at our place in a small greenhouse. I figured that our high-tech methods weren’t going to work down there, so maybe we needed to reverse engineer this to low-tech or no-tech. Mushrooms can grow on wastes such as paper and cardboard or clothing, so we started growing mushrooms on just about everything. Given that the tsunami on Christmas day just happened a year or two before, there would be debris everywhere. When we thought about what someone in that situation has to grow mushrooms in, we looked at debris and nursery containers. This could be the moment to show that, in a natural disaster or even a wartorn area, fungi could grow in little bins or modules filled with debris and watered. It wouldn’t have to be clean water, just not salt water. You add the culture, and in a couple weeks you have mushrooms growing out of these bins. The fruiting bodies are 90 percent purified water and 16 to 17 percent protein. When we went down to Haiti two years ago, we hadn’t really perfected the system yet. I went with Clemson University engineering students for developing countries. I lectured for them so they paid me to go down there for about a week. I went to a trade school up in the mountains. In the morning, with a translator, I taught them about mushroom life cycles and ecology and how mushrooms do all these wonderful things. In the afternoons we built a very primitive fruiting room with insect netting and reflective fabric that we dumpster-dived and scavenged for because we couldn’t take much with us. But not a lot of fruiting occurred. I think our growing room was in too sunny of an area, and it got so hot that the mushroom cultures might have died. Right now we’re in discussion with Clemson to plan another trip with a system that’s better designed. Now we’re looking at caves and shipping containers buried in dirt to insulate them. We will need to train someone there to understand mushrooms— someone to watch over them and keep a pulse on what’s going on. One or two little mishaps in those few weeks and all is lost. But once you get past the first three weeks of colonization, it’s easy. Haiti is a mycophobic culture. That’s a challenge. Just like in the United States, a lot of people won’t eat an oyster mushroom because they never heard of it or it looks funny. We picked some wild oyster mushrooms down there and had the local girls cook them up. They were afraid to cook them because they said there’s only one named mushroom on the island that you can eat. They’re actually surrounded by thousands of different mushroom species, a lot of them edible, and oyster mushrooms were growing right in the village. They cooked them up, and I ate them in front of them. They were watching me like I was crazy. I pulled a trick on them. I fell to the ground for a second and pretended to pass out. They started laughing when I came back over to them. Some of them tried them and said, ‘these are really good.’

ACRES U.S.A. We don’t usually eat snails here, but they’re a delicacy in France.

COTTER. Sure. Nobody likes an outsider to tell you what to eat. I think it’s going to take a bit more persuasion without being pushy. We can tell them that this could have as much protein by dry weight as chicken, and that they might want to dry it and use the powder and bake it into bread or make it into a pastry.

ACRES U.S.A. Where does using fungi for purifying water come in?

COTTER. That’s a great transition from the mushroom rescue module, which is what I call the little bins we used in Haiti to grow biomass. The myceliated or colonized block of fruiting substrate you’re producing is essentially a micron filter. You could tunnel out a little hole in the top or make a depression and gravitate water through these containers to strip out biological contaminants. It’s very easy to do. A micron filter doesn’t pull chemical pollutants out. It’s a physical trap. Chemical degradation is much different because it takes time for those chemical keys we talked about to unlock herbicides and other chemicals.

ACRES U.S.A. But is it going to filter out biological contaminants and sediment?

COTTER. A lot of the organics adhere to particulates in the water. If you can pull out the particulates, the bacteria will be removed, too. Cholera is generally not free-living. It likes to bind to chitin, which copepods are made out of. They’re tiny microscopic crustaceans that filter-feed in water. The beautiful thing is that mushroom mycelium is also made of chitin. We’re creating these biological filters with the Clemson engineering department. Next semester we’re going to construct the prototypes to take down to Haiti the following spring.

ACRES U.S.A. Would it be manufactured there?

COTTER. Yes, it’s a by-product of the mushroom production cycle.

ACRES U.S.A. It sounds like one of the challenges is the difficult climate.

COTTER. Sure. But we have tropical species. We’ll also teach people how to clone and bring back species that are native to the island.

ACRES U.S.A. Could mycelium biofilters replace a conventional water treatment plant?

COTTER. We’re not up to that yet. Fungi are aerobic and when you start flooding them with large volumes of water, they become less aerobic to do their job. To get to the next level, especially for large continuous flows of water, we are trying to figure out how long the mushroom mycelium can stay submerged, or if we need to oxygenate the water and percolate it through.

ACRES U.S.A. Is the mycelium still alive?

COTTER. There are two ways to do it. You could kiln dry and kill the mycelium and just flow water through it. Then it would be like a chitin exoskeleton. I think the magic occurs when it’s alive and self-healing, and it also reacts to the biological pollutant immediately. If the water’s chemistry and the biology changes, as a living organism the biofilter will almost immediately sweat different chemical keys or antibiotics to kill what’s coming through.

ACRES U.S.A. Let’s move on to myco-remediation. You have described fungi as “gifted and talented” at breaking down different contaminants. How have you been able to identify these traits in different fungal species?

COTTER. Every mushroom is different and every eco-type of each mushroom is different. That’s the challenge. I cannot build a house. Without a recipe, I can’t bake a cake from scratch. Just like people, every oyster mushroom that I find is different, even though they’re the same species. So we collect and clone them, and they have different genetics that can be expressed given their situation. We have to screen every ecotype of these mushrooms to see what they can do. I put them on a plate and see if they’ll eat a particular herbicide or hydrocarbon. I can see if they attack E. coli or another pathogen. Some mushrooms are extremely specific to the point of producing very unique chemical keys. They will only break down one thing but they’re really, really good at it.

ACRES U.S.A. How do fungi benefit from being able to break down weird, manmade things?

COTTER. I think it’s in their best interest. If fungi are interested in perpetuating their life cycle, I would guess if there’s something in the way that’s hard to decompose, they’re going to try to break it down so other organisms can eventually turn it back into soil. Also, they may be desperate. Maybe the strain landed there. If we don’t eat this, we can’t make a mushroom, and we’re going to go extinct. A lot of fungi have been found doing very peculiar things. Those are my favorite phone calls. That’s why I love lecturing and showing slides of weird fungi. Someone found a fungus in the Amazon that’s an endophyte, growing inside the leaves of a living plant. They isolated it up at Yale. It can eat polyurethane as its sole carbon source. Then one of the students says, let’s try it anaerobically. Guess what? It does it without oxygen, too. There are an estimated 1.5 million-plus species of fungi on the planet. We’ve only identified 150,000, and we have banked and have the DNA for 10,000. It’s up to researchers to challenge them to do things that we don’t even know about.

ACRES U.S.A. You have talked about bioremediating herbicides and other chemicals. How would you mycoremediate a contaminated site?

COTTER. It’s about contact time. Fungi are equipped to do the first level of disassembly of an herbicide molecule. Something like atrazine could be degraded to other triazines, or other different analogs. Then a secondary metabolite from that fungus may break it down a little further so it’s no longer a triazine. I would really like for people to know this because some researchers give credit to fungi for breaking down atrazine 80 or 90 percent after 30 days. Well, that’s wonderful but ….

ACRES U.S.A. It’s still toxic.

COTTER. It’s like melting down a sword and turning it into a gun. If you’re doing liquid chromatography and the atrazine is gone — yeah, but where did it go? The good thing is that, as a researcher, you find out what the secondary and tertiary degradation products are. Remember I said mushrooms are very good team players, that they collaborate? When a fungus reaches a dead-end in breaking down the atrazine, where it can do no more, it will sweat out a different metabolite that probably has some sugars in it. This will attract specific bacteria. In essence, the fungus selects its army of bacteria to perform the secondary and tertiary degradation, the next relay of the race. This is called a speciessequence. The bacteria are going to break down the chemical even more quickly because they’re extremely opportunistic in those environments, and they’re aquatic. Bacteria require at least 60 percent moisture, or water to swim and function. Fungi actually can tolerate much lower levels of moisture because they sweat their own water. As a researcher you can go back and test the soil and say honestly that the toxicity is gone. That’s mycoremediation, which is ultimately what you want. But what people should know is that in a laboratory just with a fungus alone what occurs is biotransformation. The bacteria are what make it work better in the wild than in the lab.

ACRES U.S.A. Tell me about how you use symbiotic relationships between fungi and bacteria as a mushroom grower.

COTTER. This knowledge of bacteria and fungi working together suddenly blindsided me. Now I study a lot of bacteria in the lab. At Mushroom Mountain we go from being extremely pure in the colonization room to the fruiting room, which is dirty. My problem with a super-clean fruiting room is that in a monoculture a mold or a bacterial outbreak will spread like wildfire because there’s no defense. But if you colonize a substrate and have a lot of organisms around, they’ll all be battling it out. In my fruiting room, where I have more biodiversity, there’s more harmony and balance. I have banana plants and pitcher plants, spiders and lizards and frogs jumping around. It really does work. After fungi are done, having those bacteria helps detoxify them.

ACRES U.S.A. You describe fungi as swimming in their own waste, which bacteria consume as food.

COTTER. Fungi first sweat antibiotics to try to colonize their environment and keep everybody else out. Then they transition to lay down a welcome mat for bacteria. It’s their genetic shift. They are saying what kind of waste am I sitting in here? They’ve got a really good chemical sniffer. The infantry — the outermost cells — are really chemically smart.

ACRES U.S.A. It’s incredible. But since they eat outside their bodies, their waste is just lying there. They don’t have a large intestine for it.

COTTER. They depend on bacteria to detoxify their waste products. They can’t do it themselves.

ACRES U.S.A. Do some mushrooms hyper-accumulate heavy metals and other elements?

COTTER. Most mushrooms do. Some mushrooms are better at it than others.

ACRES U.S.A. Would the heavy metals accumulate in the actual mushroom?

COTTER. Absolutely.

ACRES U.S.A. Wouldn’t that make it dangerous to eat certain mushrooms, depending on what they’re
grown on?

COTTER. Yes. Heavy metals would be the thing to look for. What’s most dangerous is trying to mycoremediate an area where the mushroom hyperaccumulates heavy metals, like in the coal ash fields. I told people planning to do this that it’s a great idea, but have they thought about what happens when the fungus pulls the heavy metals out of the environment? Now it’s magnified in the tissue, and it’s going to produce a fruiting body for whatever comes along. You’re basically making a deadly apple for the beetles and the bugs and the birds. You’re making it bio available, and it’s going to be in the food chain from then on. If heavy metals are present, you have to somehow limit wildlife activity or find a different way to process it. I think I’m going to spend the next year trying to figure out how we can do that because I want to improve how myco-remediation works. It is the most frequently asked question in myco-remediation classes. Herbicides and hydrocarbons are easy, but heavy metals are difficult because of bioaccumulation and potential bioavailability, and the disposal issue.

ACRES U.S.A. Would you feel comfortable eating mushrooms you grew on herbicide-contaminated waste?

COTTER. I would because the herbicide doesn’t cross the cell membrane to hyper-accumulate in the fruiting body. It doesn’t work that way. Heavy metals do.

ACRES U.S.A. How can fungi be used as an alternative to pesticides in controlling mosquitoes?

COTTER. That’s the third thing that the mushroom rescue modules can do. We’ve seen that these modules produce food and can filter water and biological contaminants. They also vector mosquitoes, like blood in the water for a shark, because mushrooms produce octanol, an alcohol that attracts mosquitoes. We’re partnering with someone in the Philippines on this, and we’re talking to others about collaborating. We’re looking at keeping mosquitoes away from homes and sleeping quarters so you put the mushroom modules at the edge of the village. They’re hissing out octanol at night when the female mosquitoes are out, ready to bite. They’ll go toward this huge plume of octanol in the mushroom fruiting rooms. We’re designing traps to go around the fruiting rooms. They could be adhesive traps or they could have myco-pesticides. There are fungi that mummify the mosquitoes, like Beauveria or Metarrhizium.

ACRES U.S.A. This raises the question of intellectual property rights. You’re coming up with these amazingly diverse, life-saving ideas. What position do you take on protecting them?

COTTER. I don’t think anybody should patent the mushroom rescue module idea. The use of mushroom mycelium as a filter is now public domain. There are companies that produce octanol, but I think it’s synthetic. Mushroom alcohol is much more efficient and desirable. As far as natural systems, we don’t intend to get any patents. We’re trying to get this stuff out. Someone recommended a humanitarian patent. There are a lot of things that we’re working on that we don’t talk about. A lot of people tour our farm and try to glean what they can, but there are a lot of locked doors and security cameras. I love talking about fungi and people need to know that a lot of good things are going on. Yes, we do need to be excited about it, and, yes, I do need to not give everybody all the details because somebody’s going to scarf it up.

ACRES U.S.A. The danger would be a corporation getting ahold of something and patenting it, preventing it from being used for the public good.

COTTER. That would be a shame. There are things of economic value that we’re looking at as a company. I want to own enough intellectual property to be able to see these things to fruition, whereas some companies may own the intellectual property and shelve it or just keep the products going temporarily.

ACRES U.S.A. In order to keep their life-destroying technologies on the market?

COTTER. That’s a fact. That’s not anybody being paranoid. That’s how it works. There are a lot of products on the market that, if you invent something that’s a disruptive technology companies affected by the economic disruption are going to either try to buy you out or fight the release of your product. My comfort zone is trying to solve problems, and fungi are good at that.

ACRES U.S.A. Could you lay out the crisis of antibiotic resistance?

COTTER. Fleming discovered Penicillin. Back in the 1930s he warned against it being used rampantly, only for emergencies, but we did not heed his advice. Antibiotics are derived from bacteria, fungi and plants. Then they’re synthesized and mass-produced. Everybody is taking the same thing. Humans are being prescribed antibiotics for the wrong thing, like for colds and viral infections that are not caused by bacteria. And in agriculture, livestock that aren’t even sick are medicated. Also people misuse antibiotics. They start to feel good so they stop taking their prescription and may save the antibiotic for a rainy day. But our bodies need that much time to wipe out all the bad guys. When some are allowed to linger around, they learn how to deal with the antibiotic. Those are the ones that will become resistant. So a lot of antibiotics now are ineffective against many pathogens. Bacteria are promiscuous and they will share genes. They can dock with another bacteria and upload their genes, just like a thumb drive, and pass them around. They do this not just with their own species, but even with other genera.

ACRES U.S.A. So they’re getting genes from other species that might be drug-resistant?

COTTER. Yeah. They’re sharing them so they can move in and out of gradients of antibiotics at will. Doctors and hospitals now have to prescribe cocktails of multiple antibiotics, which is extremely toxic. It’s just a matter of time before they develop resistance to that, too. Now doctors are going back to drugs that were pretty much banned as extremely toxic. The situation is pretty grave. If you look at the websites of the big antibiotic makers, like Pfizer and Merck, you’ll see that a lot of their research and development is on the pill-a-day kind of illnesses and disorders like depression. They’re not focusing on gram-negative bacterial infections as much.

ACRES U.S.A. Big pharma probably won’t be enthusiastic about the solution you have.

COTTER. No, because it really damages the profit wheel.

ACRES U.S.A. What is your approach?

COTTER. In most microbial or antibiotic discoveries, you first isolate native fungi and do extracts and streak them on plates. We do it the opposite way. We grow things in coculture and then we look for inhibitions. We also look at behavior — how fungi interact with their environment. Fungi evolved to be quick thinkers. They’re constantly sampling the environment and shifting their genetics to produce novel compounds, whether it’s an enzyme to eat something or an antibiotic to fight their way through the environment. They’re very good at shifting their assembly lines around to produce different compounds at any given moment.

ACRES U.S.A. How do you use these observations in your solution to the antibiotic resistance crisis?

COTTER. We’re creating a pharmaceutical company in a bag. In the lab we create cakes of mycelium. We put them in specialized bags we designed with two injection ports, high and low. You would inject a throat culture or a staph boil, or even a plant infection, into a little well in the bag. It doesn’t even have to be sterile. The fungus interacts with the pathogen for 24 to 48 hours and spits out highly concentrated metabolites for harvest from the other port. It would be a target-specific mixture of different compounds that the fungus decided to make against the pathogen. This would be the patient’s personalized prescription. We’ve been experimenting with this system for about a year and we keep making considerable advances. We have a process patent. Its first use could be in a hospital laboratory.

ACRES U.S.A. Given the way FDA approves drugs, wouldn’t the agency require animal toxicity tests for each compound?

COTTER. Sure. I’ve been approached about rolling it out in other countries first because of red tape. We’ve submitted a National Institutes of Health grant proposal and scored very high. We got comments from reviewers like, ‘wow, this could really be a game-changer,’ but one reviewer gave us the worst score possible. We’re going to resubmit. That was a grant for preliminary study, so, of course, we would do animal studies. Clemson University is set up to do them with drug-resistant organisms. We don’t need to bring those to Mushroom Mountain!

ACRES U.S.A. Let’s go back to what you mean when you say mushrooms are like factories.

COTTER. They’re opportunistic consumers. They are constantly adapting to the environment through their genetics. Imagine the complexity. There are tons of undescribed organisms in a gram of soil. For a fungus to be able to thread its way through the environment unscathed, it has the ability to manufacture on the spot — and bathe itself in — its own novel antibiotics. At the same time a fungus recruits beneficial bacteria. There are a lot of workers on the fungus’ assembly line that aren’t being used all the time. Some of them are skilled at making one product. From the front line, the mycelium sends a message. ‘Now we need this built, and we need it fast.’ Then those genetics get expressed and the workers jump in and start manufacturing something
completely different, and other workers take a break. It’s phenomenal.

ACRES U.S.A. In one of your talks you stated, “I’m weaponizing the planet. I need to infect things.” That sounds pretty ominous!

COTTER. I taught a class at the PASA conference. I told everybody I went militant, and they loved it. It’s time to start bombing locations with mycelium. I gave them permission. The infection process starts with education that fungi are excellent at solving problems. They’re an untapped resource. The more people are fungus-savvy, the more these problems will be dealt with on a local level.

ACRES U.S.A. That’s a great answer. Are you the originator of the idea of guerilla mushrooming?

COTTER. I think so. I haven’t seen any other record of people bombing mulch companies on a Sunday afternoon. Maybe a mulch company or a recycling facility grinds up curbside pick-up debris and storm debris. You can talk to the owners, or not. You introduce mycelium or cultured spawn to the big mother piles or put it in the tub grinder where everything gets shredded so the mycelium sticks to the blades. The mushrooms will keep perpetuating. They’ll be redistributed all over the city when people get mulch.

ACRES U.S.A. Have you seen this work?

COTTER. Yeah. Clemson University now has King Stropharia mushrooms all over one side of campus. They came from me walking around with a bag of spawn in my backpack and throwing it out there. A lot of people know it now, and they go to the university to pick mushrooms. It’s a great thing for the landscape, and it’s good for the plants. The mycelium breaks down mulch and feeds the soil. It’s wonderful.

ACRES U.S.A. Why would you put spores in chainsaw oil, or in the ink used to print on cardboard boxes?

COTTER. The chainsaw oil is a direct means of infecting stumps that you cut. It initiates the stump decomposition cycle and soil creation. It’s easy to make spore prints out of beneficial, native mushrooms and then mix the spores into a biodegradable vegetable oil and put it in your bar and chain oil. The idea of living ink, putting spores into ink or making ink out of spores, is still experimental. We’re getting ready to do that with the boxes we sell mushrooms to restaurants in. I have permission from our box company to dose the ink we’re going to use with living spores right before the run. If you wet the box, the spores will germinate, mate and then start the decomposition process. Somebody could put it in the compost pile and maybe a couple weeks later you might have oyster mushrooms coming out of your compost. It’s something fun that I’d like to be an extension of good consumerism because it self-destructs. Kids can cut it out and do projects with it. Oyster mushrooms are not only able to eat the cardboard. They also break down the adhesives in the box, which don’t compost. I would hope one day that we could use self-destructing ink en masse. Short-life print objects like newspapers are probably target number one.

oyster fungi and olivia
Olga Cotter checks out wild oyster mushrooms.

ACRES U.S.A. You suggest that single-use consumer objects could be made of mycelium. That way, discarding them would not be a solid waste problem. What are some examples of this application?

COTTER. Mycelium could be pressed or formed into things like little packaging peanuts and other packaging. Bags,
paper plates, insulation, buoys, you name it. Sue Van Hook, the mycologist at Ecovative, is working on a lot of stuff
in that respect.

ACRES U.S.A. Are there any other really peculiar things that fungi can do that might interest readers?

COTTER. We’re cultivating some fungi exclusively for their pigments. A lot of fungi make beautiful pigments. They come in every spectrum of the rainbow. They could replace chemical dyes, but no one else is looking at them. We’re expanding our collection of fungi that produce different alcohols and fermented foods like tempeh. Another area is biofuel production — the ability of fungi to disassemble agricultural wastes and free up all that cellulose for bacteria or other anaerobes to convert into ethanol or butanol is spectacular. Butanol is much cleaner burning than ethanol, and no changes in the internal workings of the gasoline engine are required to burn it. Some of my latest research is looking at those possibilities.

ACRES U.S.A. What about the medicinal applications of mushrooms and mushroom beer?

COTTER. We came up with mushroom beer years ago, and I thought it was a unique delivery system. Beer is the number one cold beverage in the world, and craft brewers are popping up like weeds. How can they differentiate themselves? Beer produces carbon dioxide, which comes in handy because fungal medicinal extracts oxidize very quickly in air, and become less effective. If you dilute them in something carbonated, they’ll store much better. The level of alcohol also helps stabilize the medicinal molecules. We do a really high-grade alcohol extraction of say reishi mushrooms, which are pretty well-known, though I can honestly say all mushrooms are medicinal. They’re all good at something, but reishi has a very complex molecular chemistry that produces a lot of compounds that are active against different illnesses and inflammation. They regulate sugar and there’s a natural antibiotic and something that stimulates your immune system and beta-glucans. These are all things that pharmaceutical companies are purifying, but we want to keep everything together in its package at harmonizing levels that a consumer can take. It’s less toxic in those forms and more target-specific. Beer, like some mushrooms, is kind of bitter. Americans don’t like to take medicine, but if you can put it in beer, I think you have a winning combination. When we did this at the Telluride Mushroom Festival in Colorado three years in a row, we couldn’t brew enough. Every year we double and triple our output, and it keeps selling out. So mushroom beer is going to be big, and we are the leaders in this industry pushing it forward.

ACRES U.S.A. One last question. Do you think like a mushroom?

COTTER. Absolutely! Today I convinced my class that they should, too. They were all smiling, and I said you’re going to wake up tomorrow feeling a little bit different. When you walk through the grocery store, you won’t be thinking about the food as much as what it’s packaged in. You’ll be morphing like a werewolf into a fungus! What’s the best way to learn a foreign language? Total immersion, right? You can learn the basics from a book or a tape, but you really have to speak the language. Every mushroom is different and their language is different so you really have to study and get to know them. I try to become fluent in their language. It’s like uncovering a biological Rosetta Stone, the more we observe and learn from fungal behavior, the values and benefits can be decoded and braided into our coexistence.

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