Preservation of Luminous Bacteria in Absence of Oxygen.

Abstract

In the course of experiments on the respiration of the luminous bacterium, Bacillus fischeri, 1 it became necessary to determine whether or not this organism was a facultative anaerobe, a characteristic assigned by Beijerinck 2 to one species of luminous bacteria.

The luminescence of luminous bacteria is absolutely dependent on the presence of a partial pressure of oxygen in the medium or the atmosphere in which they grow. 3 , 4 If all oxygen is removed from the medium, and from the atmosphere above the medium after inoculation, the organisms may be allowed to remain in quite anaerobic conditions. Preparations were made for the maintenance of luminous bacteria in absence of oxygen as follows:

A number of experimental tubes were made by narrowing the middle of the ordinary bacteriological culture tubes to facilitate sealing off after inoculation. Nutrient media was placed in the sterile tubes and the whole autoclaved. By means of short and long glass tubes passed through the tightly-fitting rubber stopper replacing the cotton plugs in the tubes, pure hydrogen was passed over the medium and out again. (It is necessary that this hydrogen be passed over hot platinized asbestos contained in a heated quartz tube and be carried to the preparation through lead tubing to prevent diffusion of oxygen into the system.) The medium was boiled to eliminate oxygen while the pure hydrogen passed through the system, cooled as a slant with the pure hydrogen passing over the medium, quickly inoculated with a vigorous growth of the luminous bacteria and replaced in the system so that the pure hydrogen might again replace all air present. With the pure hydrogen still passing rapidly through the system, the tube was then sealed off at the narrow neck, allowing the inoculation to remain in an atmosphere of pure hydrogen, and on an oxygen-free medium.