ANTIBIOTICS

An antibiotic is a chemical substance produced by a bacterium or fungus, which kills or prevents growth of another species of microorganism.

Humans have exploited these substances and their derivatives medically, in agriculture and in scientific research.

Background

The above definition of an antibiotic is too narrow. Many other organisms, including many plants, produce molecules which are toxic to other species. These may be termed antibiotics, especially if they are active against microorganisms, whether or not they have any significance in nature in this respect. The molecules present in the venom of certain tropical frogs which are currently being investigated for possible use as precursors of new antibiotics, come into this category.

Many substances related to, or derived from, naturally-occurring antibiotics are now widely used in medicine. Although synthetic, the term antibiotic is, nonetheless, widely used to describe these substances.

The well known sulphonamide drugs, though entirely synthetic, are often incorrectly (see definition above) described as antibiotics.

Background

Produced by many mould fungi and bacteria, antibiotics are thought by some to be of possible importance in ecosystems, as one of the determinants of competitive success in colonising new habitats. Despite the simplistic appeal of this idea, others are sceptical and suggest that they may merely be evolutionary vestiges of now redundant biochemicals.

Antibiotics are now routinely extracted from a wide range of microorganisms grown in culture on an industrial scale in fermenters. Many strains of fungi and bacteria have been selected for their ability to produce high yields of antibiotic, and the techniques of genetic modification are employed to produce further novel strains, and to increase yields. In addition, many antibiotics and effective molecular derivatives of antibiotics can be synthesised in the laboratory.

The distinction between antibiotics and antibodies should be stressed to students.