METABOLISM AND POPULATION CHANGES IN BRUCELLA ABORTUS I

Abstract

The selective action of D-alanine in promoting changes in relative numbers of smooth and nonsmooth types in originally smooth cultures of B. abortus strain 19 in liquid synthetic medium is antagonized competitively by L-alanine, and noncompetitively by 2 L-alanyl di-peptides. L-alanyl-L-valine reverses the activity of D-alanine which suppresses growth of smooth type cells; L-alanyl-L-leucine suppresses spontaneously arising nonsmooth mutant types. L-alanine does not suppress population changes in cultures not supplemented with D-alanine. These data contradict the hypothesis that metabolically produced D-alanine is a major selective factor which promotes population changes. During growth in Gerhardt-Wilson synthetic medium containing L-asparagine as the N source, smooth type cells synthesize and excrete pantothenic acid whereas rough type cells utilize the preformed pantothenate present in the medium. There are no quantitative differences between cell free extracts of smooth and rough cells in the kinetics of pantothenate synthesis or metabolism. Whole rough type cells exhibit a greater rate of pantothenate uptake than smooth type cells. D-Asparagine inhibition of pantothenate synthesis from pantoyl lactone and L-asparagine is greater for smooth cells than for rough cells. The relevance of these findings to the known sequence of events in population changes from smooth to nonsmooth types is discussed.