Acid-base-combining capacities of concentrated bacterial suspensions.

Suspensions of bacteria containing from a few million to several billion cells per milliliter are used in numerous phases of bacteriology and immunology. The importance of maintaining the proper hydrogen ion concentration in bacterial suspensions used for various purposes and in cultures has long been known. It has also been demonstrated that bacterial celLs exert a buffering action, and often considerable amounts of acid or base must be added to heavy suspensions of organisms to cause any appreciable change in the pH of the suspension. Shaughnessy and Falk (1924) measured the buffering action of heavy suspensions of washed cells of Escherichia coli in a water and salts solution. Recently McCalla (1941) has shown that the combination of the bacterial cells with hydrogen ions is an adsorption phenomenon. The present investigation was undertaken to compare the acid-base-combining capacities of different species of bacteria and to study the mechanisn of the buffering action.