The Method of Electrical Conductivity in Studies on Bacterial Metabolism.

The electrical conductivity of solutions depends upon the concentrations and the mobilities of charged particles of varying sizes. A culture medium in which bacteria are living and dying is a heterogeneous system, the composition and complexity of which are constantly changing. Substances in true and in colloidal solution are being chemically disintegrated and synthesized. The initial and final compositions may be well-known, but the intermediate reactions and the mechanisms involved in many cases are not understood. Several difficult problems are therefore presented in attempting to evaluate conductivity measurements in relation to bacterial metabolism. Parsons and Sturges (1926a, b) have reported a definite correlation between conductivity and the amount of ammonia and amino nitrogen produced by putrefactive anaerobes. This is the only direct relationship between conductivity and some product of metabolism which has been established so far. Others have shown, however, (Sierakowski and LQczyeka, 1933 and papers quoted therein) that there is always some relationship between change in electrical conductivity and metabolic processes even though the direct cause for the alteration in electrical field strength may be obscure. Further information on such correlations has been sought. Experiments have been done, therefore, with two different aerobic bacteria which produce ammonia, and one which produces lactic acid. It is believed that the data