Fungi play many roles, some strange and amazing

Posted: Sunday, September 16, 2007

This is a good time of year to see a wide array of fungi along Juneau's many trails. The cap on toadstools is the spore-producing part of the fungus, growing from the less visible filaments that commonly live underground or in rotting material. Perhaps the most conspicuous and easily recognized fungus in our forest is the brilliant orange chicken-of-the-woods, growing on dead and dying trees; it is edible when it is young but gets woody as it ages.

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There are probably several hundred thousand kinds of fungi; they can live in a wide range of circumstances, including a temperature range from -6 to 60 degrees C. None is able to synthesize its own food, instead depending on other organisms (dead or alive) or substances for nutrition. They can "eat" almost anything, including camera lens coatings, insulation and jet fuel, as well as plant and animal parts. Some fungi are trappers, capturing small animals such as tiny nematodes (round worms) or springtails. The filaments of some of these fungi are sticky, and the prey blunders up against them and is caught. A few fungal species "lasso" their prey in tiny ring-shaped structures that contract rapidly when a prey organism touches the inside of the ring.

Fungi as a group are so diverse that it is not surprising that they have many kinds of effects on other organisms and their surroundings. They can cause numerous diseases of plants and animals. They have essential ecological roles as decomposers, breaking down dead organic matter that would otherwise accumulate in heaps. There are the numerous mycorrhizal fungi that provide nutrition to over 80 percent of land plants, and which may well have facilitated the origin and evolution of land plants in the far-distant past. Some fungi capture algae or cyanobacteria and live as lichens.

Certain fungi can change the sex of an infected flower, or increase a plant's resistance to herbivores, or even transmit parasites to new hosts. Still others live in the guts of insects and marine crustaceans and synthesize vitamins for their hosts, and others live in the gut of mammalian herbivores and assist in the fermentation of ingested herbage. Certain bark beetles and wood wasps carry fungi in pockets on their exoskeleton to feed to their offspring. You name it - there's probably a fungus involved in some way with most other organisms.

The filaments that make up most fungi can grow at the astonishing rate of over 1 km per day. Spores of many species accomplish long-distance transport, either borne on the wind or carried by small mammals that eat the spore-bearing part of the fungus and defecate the undigested spores. Bird's nest fungi look like tiny nest cups with "eggs" inside - these are the spore capsules, each with a thread coiled underneath. When a raindrop splashes the egg out of the "nest," the coiled thread is wetted and becomes sticky. The sticky thread trails below the ejected spore and catches on the vegetation. If that vegetation is eaten by an herbivore, the spore gets an additional free ride to a new site, plus a nice rich fecal pile to grow on. Other fungi, growing in lizard and frog feces, have a different two-stage dispersal: The spore capsule pops off the main fungus, is eaten

by beetles, which are eaten by a lizard or frog, and the spores are deposited in their dung.

Although we hate fungi when mold grows on our camera lenses or causes various ailments, we also depend on fungi of various sorts for important products. For example, yeasts are used for making bread, beer, wine, and cider. Fungi in the genus Penicillium give the characteristic flavor to Roquefort and Camembert cheeses, and a related species gave us the antibiotic drug, penicillin. Other fungi are used to ferment soy beans to make shoyu (soy sauce) and tofu. Citric acid is produced commercially, not from citrus plants or fruits, as one might expect from the name, but from a cultivated fungus. Fermented livestock feed has a higher protein content than fresh feed. And many folks like to add the edible ones (carefully chosen!) to soups and pasta dishes.

A parasitic fungus called ergot infests the flowers and replaces the seeds of grasses, including domestic rye crops and our local beach rye. Ergot thrives in cool, wet weather. When infected grain is consumed by humans or domestic animals, it can cause gangrene, psychotic delusions, muscle spasms and convulsions, nervous twitches, abortion, and death. In a major episode in the Middle Ages, 40,000 people died of "St. Anthony's fire" after eating contaminated rye bread (a staple in the diet of poor folks). Before 1000 A.D., ergot poisoning weakened the resident population of coastal France, which helped the Vikings invade and take over that part of the continent. In 1722, ergot destroyed the Russian cavalry and caused the intended conquest of Turkey to fail. Historians suggest (although this is debated) that many of the women who were hanged or drowned as 'witches' were, in fact, the victims of people suffering from ergot-caused delusions. However, alkaloid compounds in ergot are also of great use in pharmacology, because they are used to induce labor, prevent post-partum hemorrhage, and relieve migraine headaches.

• Mary F. Willson is a retired professor of ecology and a Trail Mix board member.

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