Oxidation of Fatty Acids by Cell Suspensions of Spicaria Violacea

Spicaria violacea can grow in a mineral-salts solution with saturated fatty acids as the sole carbon source. Since the growth response varies with the different acids (5), attempts have been made to test the effect of these substrates on 02 uptake by the mold. The organism was grown in a Czapek-Dox medium (temperature, 30° C; pH, 7.2; carbon source, 5% glucose or glycerol; other conditions, as indicated below). Cultures were harvested by filtration, ground in a mortar with distilled water, pressed through coarse cheesecloth, and washed by centrifugation. The sediment was then taken up in distilled water to form a cell suspension which was then used for O0-uptake studies employing conventional manometric techniques. Preliminary experiments indicated the optimum temperature for endogenous 02 uptake by glucose-grown cells to be approximately 30° C; optimum uptakes were obtained at slightly higher temperatures with cells grown on glycerol. Glucose-grown cells showed high and fairly uniform endogenous rates between pH 5.8 and 7.2; glycerol-grown cells gave highest readings in a slightly alkaline range (7.2-7.6). Hence the fatty-acid effects were examined at a temperature of 30° and a pH of 7.2. Each Warburg vessel contained 1.0 ml cell suspension and 1.0 ml 0.2 M phosphate buffer, pH 7.2. The side arms contained 0.8 ml 0.1 M substrate (pH 7.2) and the center well 0.2 ml 6N NaOH. Substrates were commercial preparations of the highest available purity. The fatty acids were converted to the potassium soap with KOH in absolute alcohol, precipitated and washed with anhydrous ether, and dried in a vacuum desiccator. Cups were oxygenated for three minutes and equilibrated for fifteen minutes before the substrate was tipped into the main well.