Some Learning Goals

Know the general features that distinguish Kingdom Fungi from the other kingdoms.

Distinguish the phyla and subphyla of fungi from one another on the basis of their cells or hyphae and their reproduction. Learn the form and function of sporangium, conidium, coeno-cytic, mycelium, dikaryotic, zygospore, ascus, and basidium. Assign each of the following to its phylum and/or subphylum of true fungi: athlete's foot, Dutch elm disease, Pilobolus,

Penicillium mold, stinkhorn, yeast, ergot, chestnut blight fungus, puffball, smut.

Know five economically important fungi in each of the different major groups of true fungi. Understand how lichens are classified and identified. Learn the basic structure of a lichen.

hen it comes to breaking down organic mate-m m f f rials of all kinds and making them available for recycling, fungi and bacteria are the most important organisms known. The major oil spill that occurred in Alaska in 1989 intensified efforts to find better and faster ways of cleaning up such disasters than was possible in the past. Although there are bacteria that break down oil molecules, very few such organisms survive the salt water of the ocean for any length of time. Attention now, however, is being given to a fungus that breaks down many types of oils to harmless simpler molecules, such as carbon dioxide.

This fungus, known as Corollospora maritima, occurs naturally on almost all the beaches of the world and flourishes in ocean surf, which, as mentioned in Chapter 18, contains oils produced by diatoms. Ways of culturing the fungus inexpensively and in large quantities are being explored, and also strains that produce the oil-degrading enzymes in significantly larger amounts are being sought. This chapter examines the nature, reproduction, and other features of this and the thousands of other known true fungi found all over the world.

The word fungus may evoke images of mushrooms or some sort of powdery or spongy, creeping growth. Although mushrooms are indeed fungi, and while many fungi do appear to be creeping along the ground, the forms of fungi seem almost infinite. There are about 100,000 known species of mushrooms, rusts, smuts, mildews, molds, stinkhorns, puffballs, truffles, and other organisms in Kingdom Fungi, and over 1,000 new species are described each year. There may be as many as 1.5 million species yet undiscovered or unde-scribed, and our daily ravaging of rain forests and other fungal habitats undoubtedly is dooming many species to extinction before they can be found.

As they grow, most fungi produce an intertwined mass of delicate threads that tend to branch freely and often also fuse together. The individual, usually more or less tubular, threads are called hyphae (singular: hypha). Hyphae may or may not be partitioned into cylindrical cells (Fig. 19.1).

A mass of hyphae is collectively referred to as a mycelium. When appropriate food is available, fungi grow very rapidly. In fact, despite the microscopic size of individual hyphae, all those produced by a single fungus in one day when laid end to end could extend more than a kilometer (0.6 mile). Some fungi thrive in freezers if the temperature is not lower than -5°C (23°F), while others grow best at temperatures of 55°C (131°F) or higher.

Besides being vital to the natural recycling of dead organic material, fungi, along with bacteria, also cause huge economic losses through food spoilage and disease; these topics are explored in the sections on human and ecological relevance of fungi later in the chapter. Scientists who study fungi are known as mycologists (from the Greek word myke-tos, a fungus). Consumers of fungi are called mycophagists.

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