THE MORPHOLOGY OF BACTERIUM SHIGAE CULTIVATED ON VARIOUS MEDIA FAVORABLE TO THE DEVELOPMENT OF FILTERABILITY AND LIFE CYCLE FORMS

A simple micro motion picture apparatus has been developed which is so inexpensive to construct and to operate that it can be used regularly for bacteriological research. With this equipment about 6000 feet of film representing 600 hours of photography have been made of B. shigae growing upon various solid media. These pictures illustrate the principal phenomena accompanying the development of this organism on ordinary nutrient media, on media consisting exclusively of either peptones or proteins, and on media containing small amounts of LiCl. Information has thus been gained concerning the existence of a life cycle in the Shiga bacillus and concerning its filterability through Berkefeld filters. The formation and history of the various "life cycle forms" are recorded but the evidence does not point to them as phases of actual cycles. In "filterable" B. shigae cultures—such as those grown in the so-called "K" broth or in lithium chloride-containing media—many small and short rods are present. It has been found that these dwarfed organisms pass through filters impervious to the cells of rapidly growing normal cultures. This offers a simple explanation of "quick reversions." The present experiments do not provide conclusive information concerning the slower reversions which are supposed to occur only after many days of treatment and incubation.