82 BACTERIOPHAGES 



Phage particles inactivated by decay of P^^ can still participate 

 in cross reactivation (Stent, 1953; Stahl, 1956), indicative that 

 the lethal radioactive disintegrations destroy only part of the 

 viral genome. The details of these experiments will be con- 

 sidered in Chapter XVIII. It has not been possible, however, 

 to detect any multiplicity reactivation of phage particles in- 

 activated by decay of P^^ xhe ability to give the lytic and 

 lysogenic responses are both destroyed by P^^ decay at the same 

 rate in the temperate phages lambda and P22. 



5. Summary 



The group of physical agents whose effects on bacteriophages 

 have been considered in this chapter includes various forms of 

 radiant energy, such as visible and ultraviolet light and ionizing 

 radiations, as well as the energy released by radioactive decay. 

 In the case of radiant energy, the inactivation of phage particles 

 is seen to result from the chemical reactions caused by the ab- 

 sorption of the electromagnetic quanta, whereas in the case of 

 radioactive decay the local energy suddenly generated in the 

 vicinity of the disintegrating atom appears to be responsible for 

 the lethal effect. Inactivation by these agents is often highly 

 specific, involving only certain properties of the phage particle 

 and leaving other properties unharmed. A thorough investi- 

 gation of the mechanisms by which bacteriophage particles are 

 inactivated may reveal much information about the complexities 

 of structure and function in viruses. The results already ob- 

 tained and discussed here serve as an indication of what may be 

 accomplished. 



