DNA AND Effects of Radiation and Peroxides 283 



cumene peroxide after 15 minutes contact at 37° left 18 per 

 cent of X and 0-4 per cent of T2; 2 X 10"^ succinic peroxide 

 after 5 minutes contact at 18° left 24 per cent of lyophilized 

 T4, and 0-2 per cent of lyophilized Tl. 



Inactivation of bacteria -bacteriophage 

 complexes by peroxide 



Bacteria-bacteriophage complexes are very sensitive to 

 peroxide, especially during the first half of the latent period. 

 As soon as new intracellular mature phage is formed, the 

 infective power of the complex becomes more resistant. In 

 the following experiment, B-T2 monocomplexes were brought 

 into contact, at various times during the latent period, with 

 10 ~* cumene peroxide at 37° for 10 minutes, then diluted and 

 plated for survival (Table II). 



This situation is similar to that observed in complexes treated 

 with strongly illuminated nutrient broth (Latarjet and 

 Miletic, 1953). In this last instance, it had been found that 

 complexes which survive either u.v.-irradiation or contact 

 with illuminated broth, are damaged in such a way that their 

 latent period is lengthened, and their yield in new phage 

 particles lowered. The same partial damage has been observed 

 by Dr. C. C. Brinton in B-T2 complexes treated with sub- 

 lethal doses of cumene peroxide. 



The behaviour of the peroxide is so similar here to that of 

 radiation, that an even more specific similarity has been looked 

 for. Phage X and its indicator bacterial strain K12S are 



