THE EFFECT OF METABOLITES UPON GROWTH AND VARIATION 

 OF BRUCELLA ABORTUS 



ROBERT J. GOODLOW, LEONARD A. MIKA, and WERNER BRAUN 



Camp Detrick, Frederick, Maryland 



Received for publication June 22, 1950 



In previous work with Brucella abortus (Braun, 1946) it has been demonstrated 

 how mutation and selection can account for the progressive establishment of 

 nonsmooth types in smooth broth cultures frequently observed during prolonged 

 periods of growth. Evidence was presented that indicated that such population 

 changes, common to most bacterial species and often referred to as dissociation 

 (Braun, 1947a), involve the spontaneous occurrence of a small number of un- 

 directed variants (mutants) and their subsequent establishment within a popu- 

 lation under the control of inherent and environmental factors governing popu- 

 lation dynamics. It was also illustrated how competition between spontaneously 

 arising mutants with different selective values can produce the appearance of 

 apparently cyclic, successive, orderly changes (Braun, 19476). 



In the earlier studies it was recognized that variants do not establish them- 

 selves within growing populations until competitive conditions exist. Such com- 

 petitive conditions presumably occur when the number of viable cells (plate 

 counts) reaches a maximum, whereas the total number of cells (direct cell 

 counts) continues to increase. However, the factors responsible for the limitation 

 of the size of the viable population (i.e., the number of cells that retained the 

 ability to multiply), or the "M concentration" of Bail (1929), have remained 

 obscure. A paucity of information also exists regarding the possible influence 

 of metabolites produced by one cell type upon the establishment of variant 

 types and the role that such "association factors" (Braun, 1947a) play in popu- 

 lation changes. Zamenhof (1946) and especially Ryan and Schneider (1949) 

 obtained data in their studies with Escherichia coli that suggested an important 

 role for such postulated factors in bacterial variation. Etinger-Tulczynska (1932), 

 Neufeld and Kuhn (1934), and Mohr (1934) are among the earlier workers who 

 assumed such effects but were unable to demonstrate their metabolic nature. 

 Similarly, in studies with complex media, Braun (1946) was unable to demon- 

 strate any effect of old culture filtrates upon the establishment of variants in 

 B. abortus cultures. In contrast, in recent studies with B. abortus, in which paper 

 partition chromatography and a simple synthetic medium containing DL-aspar- 

 agine as the only amino acid source were utilized, the effect of specific cell 

 metabolites of one type upon the establishment of variant types became clearly 

 evident, and the manner in which such metabolites restrict the "M concentra- 

 tion" of the cells that produce them became obvious. The following data will 

 describe these observations. 



291 



[Reprinted by permission of The Williams & Wilkins Company from Journal of 

 Bactkriolocy 60: (3) 291-300, September, 1950] 



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