IMMUNITY AND PROPHAGE LOCALIZATION 



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TABLE 4 

 Prophage Segregation in Transduction 



Note: The transductions were performed by infecting the recipient with phage 

 PI that had been grown on the donor. The infected mixture was incubated 1 

 hour at 25°, then spread on EMB galactose agar. Galactose positive transductants 

 were isolated, purified bj^ two serial single-colony isolations and then scored for 

 the type of phage production by replica plating onto K12, K12(X), and K12(434). 

 A and B indicate strains isolated independently using the same stock of phage 

 and sensitive bacterial strain. The donor strains were all prepared from C600 

 and the recipient strains from C600 gal~. 



The results of these tests, presented in Table 4, are that nonlysogenic 

 transductants did arise when the pair K12(X), K12(434hy) was tested, 

 independently of which was the donor and which the recipient. How- 

 ever, no nonlysogenic transductants arose when the pair K12(434), 

 K12(434hy) was tested. Therefore, prophage 434 hybrid occupies the 

 434 locus. Incidentally, the absence of nonlysogenic transductants when 

 the pairs K12(X), K12(X) or K12(434), K12(434) were tested is a strong 

 argument in favor of the uniqueness of the X and the 434 loci. 



If prophage 434hy occupied the same locus as prophage 434 in K12, 

 then the same frequencies of recombination would be expected between 

 the locus of prophage 434hy and the locus of prophage X as between the 

 locus of prophage 434 and the locus of prophage X. Referring to Table 4, 

 it may be seen that when the donor was lysogenic for 434hy and the 



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