Effect of certain electrolytes on the buffering power of bacterium coli.

Abstract

In the present studies we have developed a technique for the measurement of the power of the bacterial cell to combine with hydrogen and hydroxyl ions. The bacteria show a general tendency to simulate amphoteric colloids and we have therefore measured their amphoteric property by the use of titration curves. A bacterial suspension in water or in a particular salt solution is titrated electrometrically with hydrochloric acid and with sodium hydroxide and similar titration curves are obtained for the menstruum alone. From these two sets of curves it is possible to calculate a series of “buffer ratios” by taking the quotients of the amounts of acid or alkali added to shift the PH one unit in the bacterial suspension and in the menstruum alone. Such buffer ratios have been calculated for each PH unit zone between PH 2 and PH 12. The titration cells which have been developed for these experiments are illustrated in the accompany figure. The buffer ratios for Bact. coli in distilled water, 0.725, M NaCl, 0.145 M CaCl2 and in 0.580 M NaCl + 0.145 M CaCl2 solutions are presented in Table I. 1. In distilled water suspensions of Bacterium coli show a marked tendency to resist a change in hydrogen-ion concentration in the zones of PH which are of physiological interest, i. e., PH 4-10. In more acid and more alkaline solution this buffering power is weaker and the buffer ratios approximate unity at PH 3-4 and at PH 10-11.