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Preserving Genetic Diversity in the Kingdom of Fungi

Located in the rolling parkland west of Edmonton, the University of Alberta Devonian Botanic Garden celebrates the beauty and diversity of plant life, but it also houses an important collection of living organisms of a different sort.

Each year the 75-hectare Garden attracts hundreds of visitors who explore the landscaped gardens and embrace the experience of nature in the natural areas. Many of these visitors enjoy the greenery and leave, unaware that the Garden is also home to an unusual collection that plays a leading role in preserving the diversity of a different family of organisms.

The specimens in this collection belong to a life form once thought of as primitive plants lacking chlorophyll but now possessing its own kingdom. They are fungi - mainly terrestrial organisms that typically obtain their nourishment saprophytically, secreting enzymes and dissolving insoluble organic food externally before absorption, or parasitically, absorbing food from a host.

Altogether there are more than 7,500 strains of filamentous fungi and yeast in the University of Alberta Microfungus Collection and Herbarium, housed in the Garden's Headquarters Building. A resource of international importance, the UAMH preserves fungal strains important to medicine, agriculture, forestry and industry using techniques that ensure genetic stability, The eighth largest fungal collection in the world, it is surpassed in size within Canada only by Agriculture Canada's national collection.

The UAMH collection covers all major taxonomic groups of fungi, but particular emphasis has been placed on mold fungi. In addition, says its curator, Lynne Sigler (Heard), '69 BSc, '76 MSc, there is a specialization that reflects the Collection's historical roots. Those roots stretch back to 1933 when Dr. Allan Rankin, then the U of A's dean of Medicine, hired Eleanor Silver Keeping (Dowding),'23 BSc,'24 MSc, and had her set up a diagnostic service for human fungus diseases — the first medical mycology laboratory service in the British Commonwealth.

In 1954 Keeping turned her appointment over to her assistant, J. William Carmichael, '49 BSc,'S1 MSc, who had just returned from earning a PhD at Harvard. It was Carmichael who in 1960 brought together the specimens he and Keeping had accumulated to form the University of Alberta Mold Herbarium and Culture Collection. In 1987 the collection — by then known by its present-day name — was relocated to the Garden.

Although the collection has expanded greatly, its origins continue to shape it. "Predominantly what we deal with are medically important fungi," says Sigler, an associate professor in the U of A's Department of Medical Microbiology and Infectious Diseases in addition to her UAMH duties. Each year she receives hundreds of unusual or uncommon specimens for identification. Many of these relate to a medical condition of some sort.

In 1993 the UAMH received cultures from as far away as New Zealand and Taiwan. It was also consulted on various occasions by the Atlanta-based U.S. Centers for Disease Control and by other U.S. medical centres.

There are a variety of common fungal diseases, including oral and vaginal candidiasis (yeast infections) and the various types of ringworm (a term encompassing numerous skin, scalp and nail infections and athlete's foot, the most common fungal infection of all). Increasingly, however, Sigler is dealing with opportunistic pathogens. These are fungi that are not normally infectious to humans but can infect people whose immune systems are weakened, possibly by cancer, AIDS or the use of cytotoxic drugs.

"Today what we see with the larger population of people who are immunocompromised is a tremendous diversity of the organisms that can be involved in disease," savs Sigler. But fungi, she reminds us, can also be important weapons in the fight against disease. Penicillin, for instance, is the product of a mold, and Sigler point out that it can still be produced more economically using the fungus rather than synthetic chemical methods.

Another important pharmaceutical derived from a fungus is cyclosporin, the anti-rejection drug that has made organ transplants almost routine. Cyclosporin is a product of Tolyplocadiurn niveum, a microfungus found in soil, and Sigler points out that the UAMH rates a footnote in the history of this wonder drug. After the usefulness of cyclosporin was shown, the UAMH was able to provide a strain of Tohyplocadiuni niveum capable of yielding greater amounts of the drug than did the strain originally used.

This serves to illustrate the UAMH's importance as a gene bank, capable of providing,40 fungal strains to meet a variety of needs — some not even dreamed of now. Because this requires that the genetic viability of the specimens be maintained, when the UAMH adds a new specimen it produces a dried herbarium sample, but it also takes pains to preserve the fungi in a genetically stable condition. Freeze drying works well with many strains; others can be maintained indefinitely by freezing. The current approach to maintaining genetic viability in fungi is cyropreservation using liquid nitrogen, something the UAMH has done routinely since 1989. Those fungi that cannot be viably maintained using freezedrying or cyropreservation are stored under water, in oil or—if all else fails — continuously cultured.

As a gene bank, the UAMH serves a wide variety of clients. "Someone might phone from some company and want an organism having a particular property," explains Sigler. "They might ask what kind of fungus would break down cellulose, occur naturally in Alberta and grow at certain temperatures. We would be able to recommend certain organisms, which they could then use in their experimentation."

Sigler notes that there is a great deal of interest in the use of fungi in agriculture to control both weeds and insect pests. And, oi* course, the pharmaceutical industry has a continuing interest in identifying fungi with medically useful properties. In fact, the UAMH is just completing a three-year, $60,000 contract to supply 1,000 cultures for screening by a U.S. pharmaceutical company.

Contract research helps extend the budget of the UAMH, which relies heavily on infrastructure funding from the Natural Sciences and Engineering Research Council. (NSERC also provides Sigler an individual grant supporting her investigations of the systematics and ecology of microfungi.)

Among the studies for which the UAMH has received funding recently are two of particular relevance to Alberta. The first was an NSERC-funded study of the role of microbial agents in the decay and stain of aspens. The second, funded by Alberta Occupational Health and Safety, is an assessment of airborne molds as a biological hazard for Alberta commercial beekeepers.

Sigler, who maintains the UAMH collection with the help of a half-time assistant curator, an assistant mycologist and parttime technical staff, is proud of the recognition implicit in the NSERC funding and the research contracts. "Although the fungi do not receive the same attention from casual visitors to the Garden as do the showy plants, and butterflies, the importance of what we are doing is being recognized by the scientific community."

Published Summer 1994

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