THE NATURE OF THE EFFECT OF a-ALANINE ON POPULATION CHANGES OF BRUCELLA'

Previous studies have related population changes in originally smooth cultures of brucella to the extacellular accumulation of the metabo-lite a-alanine (Goodlow et al., 1950; Altenbern and Housewright, 1951; Braun, 1952). Alanine resistant, usually nonsmooth mutants, occurring at a frequency of approximately 1 in 107 celis (Braun and Ciaccio, 1952), established them-selves in such cultures as soon as the alanine concentration had reached a critical level. By adding D- or DI-alanine to cultures at time of inoculation with alanine susceptible smooth cells, such naturally occurring phenomena could be reproduced at an early point in the culture's growth; L-alanine proved inactive (Goodlow et al., 1951a). However, even after the initial addition of very large amounts of D- or DL-alanine, smooth celLs were not inhibited until the culture was approximately 48 hours old. This indicated that the inhibitory effects of a-alanine might not be direct but that alanine might interfere with the synthesis or utilization of a substance vital for the multiplication of alanine suceptible cells. The delayed inhibitory effects of this amino acid could then be due to the prolonged utiliza-tion of stored intermediates of such vital sub-stances. Dr. Werner Maas suggested to us that a-alanine may interfere with pantothenic acid (PA) synthesis, as also indicated by previous observations with yeast (Nielsen et al., 1944). Following this lead, population studies with brucella were initiated to test whether the effects of a-alanine may have a similar relationship to pantothenic acid synthesis or utilization. Pre-vious investigators have claimed that panto-thenic acid or its precursors, pantoic acid (or its lactone) and,B-alanine, are required for growth of brucella (see Hoyer, 1950). The following data will describe the results of population studies in which the possible rela-I Portions of this paper were presented at the 1951 SAB meeting. tionship between pantothenic acid synthesis and a-alanine inhibition of bruceLa was investigated