THE POSSIBILITIES OF THE CONDUCTIVITY METHOD AS APPLIED TO STUDIES OF BACTERIAL METABOLISM

Abstract

Wider application is constantly being made of physical methods by workers in the biological field. Such methods are often easy to apply and enable a large number of determinations to be made in a minimum of time. Still wider applications of such methods would doubtless be possible if adequate interpretations of the results were available. Electrical conductivity is a simple and precise determination which has proved a valuable tool in many branches of science but which has not found any wide application in studies of bacterial metabolism. Oker-Blom used the method in the study of fermentation by B. coli and B. typhosus but failed to reach any very definite conclusions. Sturges and Rettger used the method in a study of the proteolytic activity of bacterial enzymes. The purpose of this paper is to present a resume of conductivity changes as correlated with ammonia and amino acid changes in cultures of C. sporogenes and C. flabelliferum in several media. These results were chiefly incidental to a comparative study of the nitrogen metabolism of these orgamsms. EXPERIMENTAL The conductivity equipment consisted of Leeds and Northrop instruments as follows: (a) No. 4760 Wheatstone bridge, dial, type, direct reading, range 1-100,000 ohms; (b) No. 2370-B a. c. galvanometer; (c) No. 9816 transformer. This apparatus operates on a 110 V. a. c. circuit and has a guaranteed accuracy of 0.5 per eent. The conductivity cell, shown in figure 1, was 177