BACTERIOPHAGE INACTIVATION UNDER VARYING CONDITIONS OF IRRADIATION 



which prevents the immediate reaction of reducing radicals with the phage. 

 In fact the act of formation of HgOg can be regarded as a protective mech- 

 anism against immediate action on the phage, a fact which is emphasized 

 by comparing the effects of gas treatment on HgOa formation and on phage 

 inactivation [Figure 3). To bring out the complementary nature of the 

 mechanisms of phage inactivation and HgO., formation, inactivation doses 

 [i.e. reciprocals of yields) have been plotted. The general form of the curve 

 applying to phage follows most closely that for H2O2 production at the 



.0 



,X 100 75 



;7o - 



,% 25 



50 



50 



Figure 3. Effect of gas treatment on : — 



(a) Hydrogen peroxide yield 



(b) Inactivation dose for bacteriophage SI 3 



lowest dose level used by Dr. Ebert^, which were considerably higher than 

 the phage inactivation doses. It can be seen that the full protective effect 

 of oxygen-hydrogen mixtures was obtained with small amounts of oxygen. 

 Reaction 4, viz- 



HOo ^ H+ + O2- 



is clearly dependent on hydrogen ion concentration, so that oxidation 

 yields should be greater at higher hydrogen ion concentrations, and reduc- 

 tion yields should be smaller. pH dependence is well known in various 

 radiation chemical systems, including formation and decomposition of 

 HgOa^ It was found that when phage was exposed to the indirect action of 



42 



