Abstract
Falk 1 showed that the electrophoretic mobility velocity (potential difference) of diphtheria bacilli varied according to their virulence, the more virulent organisms showing low mobility rate, while those of a less virulent nature gave a higher reading. For pneumococcus, 2 on the contrary, he found that the potential difference is higher the greater the virulence for white mice and vice versa. The sequence of decreasing potentials was shown to be Types III, I, II, IV, which follows the decreasing virulence for white mice. This work on the pneumococcus was carried out prior to the isolation of several new types from the erstwhile group IV.
Following the technique of Petroff 3 the writers undertook the dissociation of a stock strain of avian tubercle bacillus procured originally from Dr. Krumwiede of the Research Laboratories, New York City Department of Health. When the culture was planted on Proskauer and Beck medium after a suitable period of incubation at 37° C. the organism had dissociated into rough and smooth types of colonies. Representatives of each were selected and planted on glycerine agar and on Petroff's egg medium slants. After 5 generations the organisms are still truly representative of the original parent colonies from which they were taken. Other tests were performed on rough and smooth avian and bovine colonies dissociated by Dr. Petroff.
In view of the hypothesis that smoothness of colony may be an indication of virulence, while roughness may be taken as an indication of the reverse, the writers determined the mobility velocities for the two types of colonies, using the Falk slide cell technique. The growths were washed once in distilled water just prior to the experiment and the procedure was adhered to as outlined originally by Falk.
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