ABSTRACT
Fungi secrete several classes of enzymes into their microenvironment for breaking down organic material (plant litter) into oligomeric or monomeric compounds for their absorption inside the cells for extracting carbon, nitrogen, and phosphorus compounds from which the fungi synthesize proteins, nucleic acids, and phospholipids for growth to continue. Their absorptive mode of nutrition is facilitated by the secretion of a diversity of organic molecules called secondary metabolites, some of which possess toxic or antagonistic activity toward other organisms. For example, the yeasts that live in the skin of sugary fruits excrete ethanol-not for human consumption, as some may think, but to arrest the competing microšora and microfauna in their habitat. The same may be said for penicillin, an antibiotic œrst identiœed as a secretion from the fungus Penicillium notatum that acts powerfully against bacteria. Some fungi live inside the plant as endophytes in a symbiotic relationship, producing secondary metabolites that confer thermotolerance to plants and thereby perhaps mutually extending their own and that of their host plants. In the niche in which the fungi liveapproximately 10 µm around the hypha-minute amounts of such compounds may sufœce for the fungus. Man’s quest is to obtain the potentially useful compounds in large quantities for use through applications of microbiology, biochemistry, and chemical engineering, or in one single word, by biotechnology. This chapter gives a few better-studied examples to illustrate the realized as well as the perceived uses of fungi.
