Pantothenic acid synthesis by smooth Brucella abortus.

The relationship between formation of exogenous alanine and the establishment of nonsmooth variants in originally smooth cultures of Brucella abortus strains has been clearly demonstrated (Goodlow et al., 1950). Furthermore, the addition of D-alanine to smooth cultures in synthetic medium (Gerhardt and Wilson, 1948) results in earlier establishment of nonsmooth cells (Goodlow et al., 1951). Subsequently, it was found that an increase in concentration of pantothenic acid in Gerhardt-Wilson synthetic medium not only delayed and nearly eliminated the population changes of smooth B. abortus cultures but also antagonized the action of added D-alanine in selectively favoring nonsmooth types (Mika et al., 1951). The apparent interrelationships between population changes, alanine accumulation, and pantothenic acid supply prompted an investigation of the mechanism of pantothenate synthesis by the smooth type of B. abortus, strain 19, in an effort to determine a basic link connecting these factors. The data of this investigation describe conditions and substrates required for the synthesis of pantothenate by smooth B. abortus, strain 19. Both valine and a-ketoisovaleric acid are precursors for pantoate; and L-asparagine or L-aspartate yields,-alanine in this organism. The importance of stereoisomerism in the stimulation or inhibition by amino acids of various steps in pantothenate synthesis is emphasized. These results are in general agreement with those of other studies concerning synthesis of pantothenic acid and its component parts (Maas and Vogel, 1953; Lansford and Shive, 1952). Also, it has been shown that pH, substrate concentrations, and age of cells are significant factors influencing the ability of resting cells to carry out metabolic reactions terminating in synthesis of pantothenic acid. The discovery of these relationships has contributed to an understanding of selective factors promoting population changes of smooth cultures of B. abortus. MATERALS AND METHODS