98 THE PHYSICS OF VIRUSES 



only reduce enzymatic rates by a factor of two argues that there 

 must be many enzymes. So the existence of a multiple enzymatic 

 structure, capable of rapidly changing bacterial metabolism, is 

 strongly suggested by these experiments. The speculation could 

 be reduced and the validity of description increased by better 

 experimentation, which lies ahead. 



Varied Effects of X-Radiation on Bacteriophage 



In a remarkable series of experiments, Watson (1950, 1952) has 

 studied various actions of X-radiation on T-2 bacteriophage. 

 Watson's work is largely qualitative in that he seeks the nature 

 of the radiation action and is only concerned with its magnitude 

 in passing, so to speak. The studies involve many of the known 

 properties of bacteriophage, such as adsorption, ability to kill 

 bacteria, ability to multii^ly, and ability to be photoreactivated. 

 Care was taken to distinguish between primary-ionization 

 (direct) effects and indirect action as far as could be done. The 

 direct effect was magnified by irradiation in broth suspension and 

 studied first. The second paper concerns indirect action in dilute 

 synthetic medium. The effect of X-rays on the individual phage 

 properties was studied under the two limiting conditions for 

 direct and indirect action. 



The numerical following up of Watson's work with deuteron, 

 electron, and ultraviolet irradiation will be of tremendous value 

 in determining the internal structure of bacteriophage. From 

 Watson's paper the following facts can be determined. 



Adsorption. For an estimated bombardment of 1.9 X 10^' pri- 

 mary ionizations/cm^, the loss of ability to adsorb was less than 

 5%. It can be concluded that the inactivation volume for 

 adsorption is less than 6 X 10~-° cm^. It is very likely that this 

 inactivation process will turn out to be multiple hit. Valuable 

 information about the bacterial surface should result from study- 

 ing it. The molecular unit involved must have a molecular weight 

 of less than 4,000. 



Virus Activity. Measured simply in terms of virus activity the 

 inactivation volume of T-2, T-4, and T-O is 4.2 X lO^^^ cm^, 

 which is one-sixth the electron-micrograph volume. This is 



