A NEW GROWTH FACTOR REQUIRED BY BUTYRIBACTERIUM RETTGERI

Butyribacterium rettgeri is a gram-positive, nonsporulating, nonmotile, anaerobic or microaerophilic, rod-shaped bacterium that ferments carbohydrate and lactate, forming acetic and butyric acids and carbon dioxide as the main products (Barker and Haas, 1944). The fermentation produced by this organism differs from those caused by sporeforming butyric acid bacteria with respect to the absence of hydrogen production, the larger yield of volatile acids, and the smaller yield of carbon dioxide. Barker, Kamen, and Haas (1945) showed that the low yield of carbon dioxide obtained in a lactate fermentation was due to the total synthesis of acetic and butyric acids from the carbon dioxide. During the course of an investigation into the mechanism of this carbon dioxide fixation, it was found that B. rettgeri failed to grow on a synthetic medium containing lactate as the fermentable carbon source, ammonium sulfate as a nitrogen source, and inorganic salts. The addition of casein hydrolyzate (acid or enzymatically hydrolyzed), a mixture of known vitamins, and a purine-pyrimidine mixture did not promote growth. The further addition of yeast extract permitted good growth (figure 1). The following report deals with the demonstration that a new factor (B.R. factor) is required for this organism, with its occurrence in yeast extract and other materials, and with certain of its chemical and physical properties.