Studies on the Action of Sulfonamides on the Respira- Tion and Growth of Bacteria1 A. Factors Controlling the Inhibition by Sulfonamides of Carboxy-

In two previous reports, it was shown that cocarboxylase and p-aminobenzoic acid counteract the inhibitory effect of sulfathiazole on yeast and bacterial carboxylases. Whereas cocarboxylase brings about this effect without exercising any inhibitory action on carboxylase, p-aminobenzoic acid exercises the antagonistic action to sulfathiazole while maintaining a certain degree of inhibitory effect of its own on carboxylases. That is, p-aminobenzoic acid behaves as an inhibitor and thereby counteracts the effect of other inhibitors weaker or stronger than itself. In the preceding studies, the experimental conditions were such that cells, exercising carboxylase activity, could not multiply. In the present study, the antagonism between proteins and sulfonamides was investigated. Under these conditions cells multipled; and growth was estimated from measurements of turbidity with the Klett-Summerson photoelectric colorimeter. To correlate the weight of cells with their carboxylase activity at a given time, the bacterial turbidity was measured immediately after the last manometric reading. To obtain approximate values, the averages of initial and final numerical values were calculated. They are given in the following tables. These, no doubt, do not represent absolute values. However, since, in a study of this nature, only the comparative values are of significance, the expressed average results do not involve errors of a serious nature.