Microbic Dissociation

Abstract

The studies of dissociation of R and S colonies in various types of microorganisms suggested an investigation of a similar nature with the tubercle bacillus. Here we encounter many difficulties. Workers with tubercle bacilli are aware of the fact that it is almost impossible to prepare a suspension free of clumps and that there are very seldom individual organisms in the suspension. Secondly, as the organisms develop very slowly, sometimes requiring four weeks for a visible colony to appear, contaminations are liable to occur and spoil the investigations of even the most careful workers; and thirdly, it is almost impossible sometimes to prevent dehydration of the culture medium upon which the organism is cultivated. When the tubercle bacilli are cultivated on media prepared in Petri dishes contamination occurs in a large number of the plates. These contaminations are not due to the initial exposure during the seeding, but to the leakage of the air within the plates. In the incubator temperature the air is expanded and again contracted when the Petri dishes are removed to room temperature where the air rushes into the plates, carrying along the contaminating molds and other organisms.

In the following study we have used for subculturing the tubercle bacilli the author's gentian-violet-egg medium made up in Petri dishes. (The procedure for preparation of the medium and inspissation can be found in any text book.) The suspension of the organism was prepared as follows: Individual colonies were removed from the original culture and triturated with platinum wire on the inside wall of a small tube containing 2 cc. of sterile salt solution with a pH of 7.8. After trituration was completed, the tubes were rotated until all of the masses of the organism were dispersed in the salt solution.