RT Journal Article SR Electronic T1 THE EFFECTS OF ORGANIC ACIDS ON THE OXIDATIVE METABOLISM OF INTACT AND DISRUPTED E. COLI JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 299 OP 305 VO 132 IS 3 A1 N. Weiner A1 P. Draskóczy YR 1961 UL http://jpet.aspetjournals.org/content/132/3/299.abstract AB Mandelic acid, hippuric acid, lactic acid, and acetic acid have been shown to inhibit the oxidative metabolism of Escherichia coli. By varying total concentration of acid and pH, a correlation between inhibitory effect and concentration of unionized molecules has been demonstrated. The concentration of unionized molecules required to inhibit oxidative metabolism 50% is approximately the same as that required for antiseptic action. The oxidative metabolism of cell-free supernatants obtained from ultrasonically disrupted E. coli is also sensitive to the actions of organic acids, but the inhibitory effect is proportional to the concentration of ionized (or total) acid. It appears that the organic acids enter the cell in the unionized form and dissociate within the bacterium to the ionized form, which is capable of interfering with intracellular oxidative metabolism. The degree of this dissociation is dependent on the pK of the acid and the intracellular pH. Thus, in the intact bacterium, the inhibitory effect is related to the concentration of unionized acid in the medium, the pK of the acid, and the intracellular pH. Conversely, knowing the concentration of unionized acid required to inhibit intact bacteria and the concentration of ionized acid required to inhibit disrupted bacteria to the same degree at a particular pH, a value for intracellular pH can be calculated. For E. coli, intracellular pH has been determined to be approximately 5.6.