VOL. 10 (1953) NUCLEIC ACID TRANSFER 44I 



5. Most of the transmitted ^^p is incorporated into the early finished phage. An 

 increase by a factor 2 to 3 in the phage yield per infected cell can be obtained in lysis 

 inhibited cultures ; such an increase in yield does not significantly increase the transfer. 



6. The "second generation experiments" previously published (Maal0e and 

 Watson*) show that uniformly labelled parental particles transmit phosphorus to all 

 parts of the progeny particles which in turn become uniformly labelled. 



7. Phage heavily damaged by X-rays or excluded from growth by the simultaneous 

 presence of an unrelated phage transfer part of their nucleic acid. Isotope transfer is, 

 therefore, not necessarily connected with the transfer of genetic specificity. 



It is well known that infecting particles cannot be recovered by artificial lysis at 

 any time during the first half of the latent period (Doermann"), and it is now firmly 

 established that the nucleic acid components, phosphorus, adenine and guanine, are 

 incompletely transferred from the infecting particle to the progeny. The transfer experi- 

 ments, and especially the observation that chemical transfer may occur in the absence 

 of genetic transfer, might, therefore, be viewed as evidence for an obligate and extensive 

 breakdown of the infecting particle soon after adsorption. There is no doubt that such 

 a breakdown can occur as evidenced by the unspecific transfer from radiation damaged 

 or excluded phage (7). In both these cases, however, transfer takes place under abnormal 

 conditions where the transferring particle does not participate in the reproduction 

 processes. It is therefore unwarranted to conclude from these experiments that phos- 

 phorus is always transferred via genetically unspecific structures. 



As they have turned out, the existing data on nucleic acid transfer, including the 

 second generation experiments, do not decide whether transfer occurs via extensively 

 degraded parental material or via large, genetically specific units. The data even fit 

 with the assumption that nucleic acid structure of the infecting phage remains intact 

 during replication and with a probability of about 50% becomes infective again and 

 reappears among the progeny. 



ACKNOWLEDGEMENTS 



This investigation has been generously assisted by funds from the Danish Society 

 for Infantile Paralysis and by the William Waterman Fund for the Combat of Dietary 

 Diseases. The synthesis of the ^^C-adenine by Drs. M. Clark and H. M. Kalckar was 

 made possible by a grant to Dr Kalckar from the Lederle Laboratories Division of 

 the American Cyanamid Company. We are also grateful to Dr A. H. Doermann for 

 supplying us with the purine requiring strain of E. coli, to Dr Dean Fraser for a most 

 generous gift of anti-T3 rabbit serum, and to Dr R. Latarjet for putting the X-ray 

 facilities of the Laboratoire Pasteur de ITnstitut du Radium, Paris, at our disposal. 



SUMMARY 



a. When ^^p-iabelled phage reproduce in unlabelled coli bacteria a maximum of 40-50% of 

 their label is transmitted to the phage progeny. Only 5-10% of the label stay associated with bacterial 

 debris after lysis: the remaining about 40% appear as non-sedimentable material in the lysate. 



b. The maximum transfer-values are very reproducible provided that all phages adsorbing on 

 a given cell do so within about 2 minutes, and that the entire progeny is accounted for. 



c. Experiments with T2, T3 and T4 all show a maximum *^P transfer of 40-50%. The same 

 phages labelled with i*C in the purines yield identical transfer-values. 



References p. 442. 



114 



