Bacteria

Bacteria were unknown to man until the invention of the optical microscope and were first observed, along with Protozoa, by Antonie van Leeuwenhoek in 1675. However, they were not scientifically studied during the following 200 years and indeed as a science, Bacteriology is only a little more than 100 years old. Pasteur and Koch laid the basis of the modern science, and the late 1800s saw the discovery, description, and formal classification of most of the species of bacteria recognized to‐day. It is a very rare event now to discover a ‘new’ bacterium: the aetiological agent of Legionnaires' Disease, Legionella pneumophila, is, however, one such example, much in the current news.