Stimulation of Bacterial Metabolism by Bacteriophage. ∗

Abstract

Examination of an automatic cinematographic record of the progress of lysis of B. coli in the presence of bacteriophage suggested that addition of phage to pure cultures of B. coli causes an increase in the rate of cell division as compared with the rate of division maintained by the same cultures in the absence of bacteriophage. 1

This growth stimulating effect of bacteriophage was again observed in a very striking way, when the phage and bacteria were brought together on solid medium under circumstances which precluded the free lysis of bacteria. Under these conditions the density of bacterial growth was markedly increased under the drops of bacteriophage.^{2, 3} These and subsequent observations lead us to conclude that the effect exerted by phage is primarily that of acceleration of the metabolic activities of susceptible bacteria (including the increased rate of multiplication) and that actual lysis, while the most striking feature of the phenomenon, is in fact only secondary in importance and occurs only as a result of this change in the metabolic rate and the consequent osmotic changes in the cells taking place if free water happens to be available.^{4, 5}

The increase in the rate of multiplication of bacteria in the presence of phage has been observed by many investigators. However, in most instances the evidence was more or less indirect. More recently there appeared two accounts of experiments in which the authors attempted to count bacteria directly and concluded that the addition of phage does not cause acceleration of growth.^{6, 7}

In view of the manifest importance of this question in connection with the proper understanding of the mechanism of the transmissible lysis we decided to carry out further experiments.

Two flasks, each containing 200 cc. of broth (pH 7.4), received a suspension of bacteria so diluted that the initial count in the flask approximated 10⁵ organisms per cc.