ACTIVE FROM INACTIVATED BACTERIOPHAGE 115 



ones (the latter carrying enough lethal hits, so that reactivation does not 

 occur among them) fail to liberate active phage. This suppression of active 

 phage production is evident for multiplicities 5 or higher of inactive phage T4, 

 and for multiplicities 8 or higher of inactive phage T2. The suppression is in- 

 dependent of the time allowed for adsorption of the phages. It may in part be 



Table 6 



The yield of active phage from bacteria in which reactivation lakes place 



accounted for by the limitation phenomenon described by the junior author 

 (Dulbecco 1949a) ; 



(c) for those bacteria that liberate active phage, the yield per bacterium is 

 not affected by the presence of inactive particles, but remains the same as in 

 controls without the inactive phage; 



(d) when bacteria are infected with several heavily irradiated particles 

 that do not give reactivation, and a few minutes later with one active particle, 

 suppression of phage production occurs in a proportion of bacteria that 

 increases with the interval between infections. Suppression is evident with an 

 interval of 2.5 to 4 minutes and practically complete after 10 minutes. These 

 time intervals between infections are, of course, averages, since infection may 

 occur earlier or later for individual bacteria in the same mixture. The yield 

 from those bacteria that liberate phage still remains normal. 



The suppression of active phage reproduction by inactive phage in excess 

 indicates the existence of some type of "mutual exclusion" between particles 

 of the same phage. Such exclusion is also indicated by the experiments of 

 Dulbecco (1949a). 



More detailed analysis of the interaction between active and inactive 

 phage, using genetic markers, will be reported in future papers. Our results 



288 



