The Stimulation of Yeast Proliferation by Pantothenic Acid

Pantothenic acid, discovered by Dr. R. J. Williams, has been shown to stimulate the growth of a number of strains of yeast (1). The amount of the stimulation depended on the strain of yeast used and some of the yeasts grew still more rapidly when inosite or crystalline vitamin B, or both were also present in the culture medium (2). Dr. Williams has generously shared with me some of the pantothenic acid in the form of its calcium salt (10 per cent calcium pantothenate), and, while this is not a pure substance, the pronounced effects of it invite experimental analysis. The yeast used in the following experiments is a pure strain of Saccharomyces cerevisiz, Hansen obtained from a single cell isolation in 1928 and which has given consistent growth since then (3).’ Williams’ culture medium was used and the methods and technique employed have been described in detail elsewhere (4). Concentrations from 0.05 to 1 microgram of pantothenic acid were added to 10 ml. portions of Williams’ original medium, and the yeast growth was measured by counting the number of cells per unit volume of medium or by measuring the density of the population with a photoelectric nephelometer. The early growth was greatest with a concentration of 0.2 microgram per ml., but a slightly higher concentration of 1 microgram prolonged the stimulation, as shown in Table I. Smaller amounts of the pantothenic acid were inadequate and greater concentrations seemed to be toxic. The addition of 1 microgram of inosite and 0.1 microgram per ml. of pantothenic acid gave an increased growth of 25 per cent at 22 hours after seeding. The