Abstract
The striking pharmacological effect of administering insulin to a diabetic person suggests that a similar response might possibly be induced in cultures of bacteria that do not utilize glucose, provided, of course, that insulin alone, and no supplementary factor, is responsible for the phenomenon.
Four organisms that do not utilize glucose (or any other carbohydrate) were tested with this possibility in view. They were Bacillus alcaligenes, Micrococcus catarrhalis, a vibrio isolated from a diseased alimentary tract, a previously undescribed coccus. None of these microbes induces measurable chemical changes in glucose, so far as available methods indicate.
Plain glucose and glucose-insulin broths were prepared, and inoculated with parallel amounts of the respective organisms. Incubation was practiced for 6, 24, 48 and 72 hours respectively. At these several intervals the various media were examined for evidence of fermentation, that is, for change in hydrogen ion concentration, titratable acidity, and for gas formation. None occurred. The reaction changes were uniformly toward the alkaline side, indicating the utilization of the protein constituents for energy. In other words, insulin failed to induce these non-glucose fermenting organisms to utilize the sugar.
Shortly after these observations were completed, Noyes and Estill 1 reported experiments indicating that insulin increased the rate of fermentation of glucose, when it was added to cultures of Bacillus bulgaricus and Bacillus acidophilus. Their procedure was to add to a milk-broth-glucose solution some insulin, and, with suitable controls without insulin, observe the titratable acidity at suitable intervals. They reported that a 20 to 25 per cent increase in acidity was detectable in cultures of Bacillus bulgaricus, considerably less in corresponding cultures of Bacilluls acidophilus, where insulin was used.
These experiments were repeated, following the technique of Noyes and Estill, but with negative results.
Get full access to this article
View all access options for this article.