REGULATION BY COLIPHAGE LAMBDA OF THE EXPRESSION OF THE CAPACITY TO SYNTHESIZE A SEQUENCE OF HOST ENZYMES

Abstract

Evidence is.presented for genetic regulation in Escherichia coli of the inducibility of galactose-1-phosphate uridyl transferase, inducibility being dominant over constitutivity. The determinant of inducibility is transduced by lambda phage and is therefore presumed to be located within the "gal" region. If the gene for transferase synthesis is present in the prophage, induction of phage multiplication in lysogenic cells causes a rise in transferase activity to levels higher than are attained by enzyme induction with D-galactose or D-fucose. Smaller enzyme increases upon prophage induction occur when the transferase is present in the host cell chromosome. Induction of normal lambda increases the differential rate of synthesis of the enzymes determined by the "gal" region of the host, viz. galactokinase, galactose-1-phosphate uridyl transferase, and uridine diphosphogalactose 4-epimerase. Studies of lambda-related phages suggest that prophage localization site is important in determining the effect of phage induction upon the subsequent activity of gal enzymes. The hypothesis is offered that an interaction between the operator locus of the bacterial gal region and a portion of the phage genome is responsible for the effects of phage induction upon gal region enzyme levels.