VmUS-INDUCED ACQUISITION OF METABOLIC FUNCTION 25 



TABLE I 

 Exclusion of active dCMP hydroxymethylase in E. coli 



** 1 mg. of protein ^= 5.6 X 10^ cells. One molecule of enzyme (TN 125) per 

 cell would produce 2.3 X 10-^ micromoles of dHMP per mg. of protein per 20 

 minutes. Formaldehyde — C^^ was used at 7 X 10^ cpm per micromole. 



at 15 minutes ) , since each infected cell can give rise to virus contain- 

 ing HMC. Several possibilities can be visualized concerning the ap- 

 pearance of the enzymatic activity. 



1. The virus injects the enzyme. In addition to the fact that w^e 

 have been unable to detect enzyme in disrupted virus preparations 

 ( Flaks et al., 1959 ) , it can be calculated that the weight of the enzyme 

 found in infected cells ( 7 x 10"^^ gm. ) approximates the entire weight 

 of a T-even phage (5-7.5 x 10"' gm. ). This hypothesis does not appear 

 reasonable. 



2. The enzyme is present in uninfected bacteria in an inhibited 

 state. We have disrupted bacteria in a variety of ways without reveal- 

 ing enzymatic activity. In addition, we have mixed and incubated ex- 

 tracts of infected and uninfected cells without inhibiting enzymatic ac- 

 tivity or producing an increase in this activity ( Flaks et al., 1959 ) . This 

 shows the absence of excess inhibitor in uninfected cells and the ab- 

 sence of a system in extracts of infected cells capable of activating the 

 hypothetical inhibited complex in uninfected cells. 



3. The enzyme is synthesized after insertion of the phage contents 

 into the bacterium. The conditions required for the appearance of the 

 dCMP hydroxymethylase bear on this hypothesis. 



a. Infection must be effected with a T-even phage; enzyme is not 

 formed during infection with other T phages, such as Tl or T5, 

 or after induction of a lysogenic system such as K12-lambda 

 (Flaks et al, 1959). Thus infection with HMC phage is re- 

 quired for the development of the activity. 



