INHIBITION BY GLUCOSE OF THE INDUCED SYNTHESIS OF THE β-GALACTOSIDE-ENZYME SYSTEM OF ESCHERICHIA COLI . ANALYSIS OF MAINTENANCE

The observation has been made repeatedly that the induced synthesis of many different enzymes can be inhibited by a wide variety of carbohydrates (Benzer, 1953; Cohn, 1957, 1958; Epps and Gale, 1942; Gale, 1943; Happold and Hoyle, 1936; Herzenberg, 1958; Monod, 1941, 1947, 1956; Monod and Cohn, 1952; Neidhardt and Magasanik, 1956). One of the most characteristic and potent of these carbohydrate inhibitors is glucose. As a result the general phenomenon has been called the glucose effect (Cohn, 1956; Cohn and Monod, 1953). During an investigation of the glucose effect, it was observed that under certain conditions a remarkable situation arose: two bacterial populations of identical genotype growing under identical conditions could be maintained indefinitely with different phenotypes; one population produced f3-galactosidase whereas the other did not (maintenance). Furthermore, a heterogeneity with respect to the induced synthesis of ,B-galactosidase simulating genetic differences could be provoked within a growing population of otherwise identical cells. An investigation of maintenance as well as of heterogeneity in the ,B-galactoside-enzyme system under conditions of low inducer concentration has been described by Novick and Weiner (1957). The Novick-Weiner effect and the one to be analyzed here prove to be aspects of the same situation. Our studies will be described in three papers.