Forest dwellers long ago discovered the value of medicinal mushrooms for the healing of both the body and the forest. Sadly, most of our ancestors' empirical knowledge is lost, but what little survives hints at a rich, albeit vulnerable source. Unfortunately, as loggers cut down the old-growth forest, many fungi lose their foothold in the ecosystem. Preliminary studies on mushrooms have revealed novel antibiotics, anti-cancer chemotherapeutic agents, immunomodulators, and a slew of active constituents.

Despite recent medical advances, microbes—especially viruses—continue to kill millions of people, stimulating the search for new antimicrobial agents that are safe for humans to use. Mushrooms, which naturally produce a surprising array of antibiotics, may provide the answer.

Mushrooms share a deeper evolutionary history with animals than with any other kingdom, so humans and mushrooms share risks of infection from some of the same microbes. Although mycelium (the network of filament in fungi) has just a single cell wall protecting it from hundreds of millions of hostile microbes in every gram of soil, it manages to form networks extending, in some documented cases, thousands of acres and weighing thousands of tons. Nutrient-rich mushrooms, before spores are created, resist infection and rot, and I believe each mushroom species predetermines which bacterial colonies can live upon it. How do mushrooms do this? The cell surface of mycelium "sweats" out antibiotics and many mushrooms target specific species of bacteria.

Useful antibiotics isolated in mushrooms include calvacin from giant puffball mushrooms, armillaric acid from honey mushrooms, campestrin from meadow mushrooms, coprinol from inky caps, ganomycin from reishi mushrooms, sorolin from turkey tail mushrooms, and agaricin from agarikon mushrooms. With a diversity estimated at over 140,000 species, mushrooms are a promising resource for new antibiotics and they are a hot topic right now with medical researchers. Mushrooms are the subject of clinical studies that examine their usefulness in adjunct therapies used as a complement to conventional medicine. So far researchers have found that mushrooms contain protein and carbohydrate compounds such as polysaccharides, glycoproteins, proteoglycans, ergosterols, triterpenoids, enzymes, acids, and antibiotics that when used individually and in concert can stop infection. Scientists have also found that each species of mushroom has a signature architecture and defense against microbes.

That medicinal mushrooms have been ingested for hundreds, and, in some cases, thousands of years, strongly suggests most are not toxic and research supports them as likely candidates in our search for natural antiviral agents. Researchers (Suzuki, 1990) discovered an antiviral, watersoluble lining in an extract of the mycelium of shiitake mushrooms isolated from cultures grown on rice bran and sugarcane base. Scientists (Collins and Ng, 1997) identified a chemical from turkey tail mushrooms inhibiting HIV type 1 infection, while others (Sarkar 1993) identified an antiviral substance extracted from shiitake mushrooms.

People whose immune systems are compromised by a respiratory virus can become infected by bacteria such as Streptococcus pneumonia. Mushrooms having both antiviral and antibacterial properties may prevent such opportunistic infections. Mushrooms also influence populations of bacteriophages—viruses that use bacteria as incubators and vectors for further infection. I hypothesize that studying the interrelationships between mushrooms and their related bacteria, viruses, and bacteriophages will reveal medically significant antibiotics in the near future.

With airline passengers from remote regions of the world concentrating in airports and traveling to far-flung destinations, contagious passengers are likely to infect others. Virtually anywhere humans congregate provides opportunities for contagions to spread, whether by air or by physical contact. With the threat of bioterrorism from weaponized viruses, a readily available, inexpensive, broad-spectrum antiviral antidote would serve the public's health. Mushrooms, especially combinations of mushrooms, offer protection from infectious diseases in at least three ways: first, directly as antimicrobial agents (antibiotics); second, by increasing your immune system's natural defenses, what physicians call the host-mediated response; and third, the custom construction of mycelia mats for filtration can reduce the risk of infection from environmental sources such as sewage from feedlots and slaughterhouses. The key is to match the mushroom with the pathogen.

Rarely in the natural world are there organisms whose use can be pivotal in addressing the many causes of disease. Mushrooms stand out. Our mandate is to engage these fungi as allies. Not only are they essential for bolstering the food web by increasing sustainability of soils, but their mycelia and fruit bodies produce a gamut of highly potent products, medically beneficial to the environment and all of us creatures living within