Biofilms in Medicine

In 1862 Louis Pasteur introduced the “Germ Theory of Disease.” Subsequently the study of microbiology has flourished greatly and its medical significance has continuously grown. Many microbial organisms implicated in disease have been identified and studies. A general science of medical bacteriology has been determined and is widely taught. Such study has been largely based upon the activity of individual free-swimming (planktonic) cells and colonies that they form. However, microorganisms often form communities called biofilms which can have properties that very different from their planktonic predecessors. Biofilms are mucoid aggregates of microorganisms which tend to grow on surfaces exposed to water. Biofilms are not the only form of microbial cell aggregate but are distinguished from other aggregates by specific properties. Another form of microbial aggregate is the familiar bacterial colony. Colonies tend to feed on their undersurface and utilize the gaseous surface above for gas exchange; they are usually clones of a single preceding cell (Wimpenny 2000). Biofilms are characterized by their locations at phase boundaries (ibid.) and their production of Extracellular Polymeric Substance or EPS. The sliminess of biofilms is due to their enveloping EPS matrix. The phase boundary at which biofilms generally form is Solid: Liquid (there are a few examples of biofilms growing at other phase boundaries but they tend to have industrial or environmental applications). An additional characteristic of biofilms which is 32 not generally cited in their description is the strong alteration of their cell physiology from that of planktonic cells (Donlan and Costerton 2002)