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J Bacteriol. 1969 April; 98(1): 131-142
Copyright © 1969 American Society for Microbiology. All Rights Reserved.

Effect of Growth Rate on Histidine Catabolism and Histidase Synthesis in Aerobacter aerogenes¹

^a Department of Biological Sciences, Purdue University, Lafayette, Indiana 47907

ABSTRACT

A study was made of how the catabolism of a carbon and energy source is affected by the biosynthetic demands of growing bacterial cells. Cultures of Aerobacter aerogenes in L-histidine medium were grown in a chemostat at rates determined by the supply of either sulfate or a required amino acid, L-arginine. It was discovered that the rate at which these cells grow under a biosynthetic restriction determines both the rate and the pattern of histidine degradation. (i) Histidine catabolism is partially coupled to the growth rate. This coupling is achieved by catabolite repression of histidase (histidine ammonia lyase; EC 4.3.1.3.), and also by a slightly decreased in vivo function of this enzyme at low growth rates. (ii) The looseness of the coupling results in a direct relationship between growth rate and growth yield, and possibly is correlated with an altered pattern of carbon flow from histidine. (iii) Sudden decreases in growth rate cause total repression of histidase synthesis for substantial periods of time. (iv) Sudden release of biosynthetic restriction leads rapidly to an increase in the functioning of the cells' complement of histidase, an increase in the rate of synthesis of this enzyme, and an increase in the growth yield from histidine.

² Present address: Miami Valley Laboratories, Proctor and Gamble Co., Cincinnati, Ohio 45239.

¹ These studies are taken from a thesis submitted by D. E. J. in partial fulfillment of the requirements for a Ph.D. degree at Purdue University, 1966. Part of this work was presented at the Annual Meeting of the American Society for Microbiology, Cleveland, Ohio, 1963.