Micro-organisms are generally grown in the laboratory in nutrient-rich medium containing large amounts of sugars, nitrogen, phosphorus and other nutrients which are considered essential for their growth. Modification of these conditions on an industrial scale provides an ideal environment in which micro-organisms can produce large quantities of useful products such as antibiotics, biochemicals, and enzymes. Natural environments, in contrast, contain only trace amounts of nutrients. Micro-organisms which are adapted for growth under these conditions are called oligotrophs. Many bacteria and fungi can grow as oligotrophs by scavenging traces of nutrients from solution or from the atmosphere. The ability of micro-organisms to grow in this way has a number of important biotechnological, medical and environmental implications.