Abstract
A pure culture of Proteus mirabilis, a bacterial species belonging to the Enterobacteriaceae family of the Eubacteriales order, was isolated from a clinical source. The organism was then serially transferred on to ten randomly-selected laboratory media and the cultures held at temperatures ranging from 20-37'C. for a period of three months. The conditions of culture and incubation were thus varied markedly, yet remaining favorable enough at times for hundreds of bacterial generations to occur. After 62 serial transfers, 30 biochemical and anti-biotic sensitivity characteristics had not changed from those initially observed except for a minimal and variable response to Penicillin G. This simple experiment demonstrates that with living organisms, the principle of "'like yielding like" holds true under a great variety of conditions over a tremendous number of generations.