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FRANgOIS JACOB 



TABLE 3 

 Transfer of NOiXLYSOGENY 



Acceptor bacteria P678 lysogenic for one of the three prophages — 82, X, or 434 — 

 and resistant to the homologous phage were infected with a preparation of phage 

 363 grown on nonhsogenic K12. After plating on various selective media, col- 

 onies were tested for their ability to release the original phage, 82, X, or 434. 



with a preparation of 363 grown on prototrophic nonlysogenic bacteria. 

 Infected bacteria were plated on various selective media, and colonies 

 were tested for their ability to release the phage of the parent strain 

 (82, X, or 434). The results of such experiments are reported in Table 3. 

 It is seen, on the one hand, that among the T^, L+, or Lac^ colonies 

 none was found to be nonlysogenic. On the other hand, a small fraction 

 of the Gal^ clones was found to be nonlysogenic, the proportion of non- 

 lysogenic clones depending on the nature of the prophage involved 

 This result is in agreement with bacterial recombination experiments 

 which show that each of these prophages exhibits a different linkage to 

 the Galh locus. 



A question raised by the transduction of nonlysogeny is whether only 

 a piece of the prophage can be replaced by an homologous region of 

 nonlysogenic bacteria. Such a partial substitution could eventually result 

 in an immune defective clone, i.e. a clone in which bacteria possess a 

 fragment of the prophage which does not allow the synthesis of infective 

 particles, but prevents phage multiplication after infection with homol- 

 ogous particles. In order to detect such clones, transduction of non- 

 lysogeny was also performed on lysogenic bacteria able to adsorb homolo- 



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