MUTANT OF AEROBACTER AEROGENES LACKING GLUCOSE REPRESSION

Abstract

From the wild strain of Aerobacter aerogenes 1033, a mutant has been isolated in which glucose does not exert its customary inhibitory effect on the synthesis of in-ducible catabolic enzymes (e.g., histidase and B-galactosidase). Substances other than glucose, e.g., glycerol and gluconic acid, continue to exert their characteristic inhibitory effects on the formation of histidase by the mutant. The biochemical lesion appears to be the inability of the mutant to form a major degradative system for glucose. Glucose degradation in the mutant proceeds at only 35% the rate in the wild strain; growth of the mutant on glucose, however, occurs at 66% the rate of the wild type, indicating that the mutant degrades glucose at a rate more commensurate with the anabolic capacity of the cell than does the wild strain. These observations strongly support the concept that the "glucose effect" is due to an excessive rate of glucose dissimilation, which builds up various repressors of enzyme biosynthesis. The repressor hypothesis is examined in the light of other recent observations.