REVERSAL OF THE GLUCOSE INHIBITION OF HISTIDASE BIOSYNTHESIS IN AEROBACTER AEROGENES

Abstract

In a wild strain of A. aerogenes,reversal of the inhibitory effect of glucose on the induced biosynthesis of bacterial enzymes was accomplished by substituting L-histidine for ammonium sulfate, the customary N source of the glucose medium. In a mutant strain of this organism which requires glutamic acid for growth, L-histidine was substituted for glutamic acid as the growth factor in a glucose-containing medium. In both cases the production of histidase was a prerequisite for growth, and both conditions resulted in growth of the cells and production of close to 40% of their full complement of the entire histidase series of enzymes, with no quantitative alteration in glucose metabolism. Addition of ammonium sulfate to a culture of the wild strain, or of L-glutamic acid to the mutant, resulted in immediate cessation of histidase formation. Comparison with the observed effects of amino acids and other supplements on the formation of the enzymes which lead to the production of these substances, it is concluded that the glucose effect is an indication of the existence of feedback mechanisms by which the levels of intermediary metabolites control the synthesis of catabolic enzymes.