TRANSDUCTION OF LYSOGENY IN ESCHERICHIA COLI 209 



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Fig. 1. Plaques formed on E. coli K12 lj\- (A) piuige '663, (B) phage 82, (C) phage 

 Xms, and (D) phage 434. 



The acceptor strain was a derivative of W677 (Lederberg, 1947) pre- 

 pared by Dr. E. L. WoUman. This strain, called P678, is unable to syn- 

 thesize threonine (T"), leucine (L~), or vitamin Bi (BY) or to ferment 

 lactose (Laci), xylose (Xyl~), mannitol {Man~), maltose (Mal~), or 

 galactose (Gait, Galh). It is not lysogenic for X (X)~ and is resistant to 

 streptomycin (S"). The Gah marker of this strain is closely linked to the 

 X locus. Its relationship to other galactose loci in the same region is 

 unknown. 



Substrains of K12 and P678, lysogenic for one or more of the four 

 prophages (363, 82, X, and 434), have been isolated. In the description 

 of the following experiments, P678(X)+ will refer to a substrain of P678 

 lysogenic for X. Variants resistant to one or more of the three phages 

 have also been used: P678/X will refer to a variant of P678 resistant to X. 



Preliminary crosses between GalhS^Hfr, nonlysogenic, and GalhS''F~, 

 lysogenic for one of the prophages, indicate that both prophages 82 and 

 434, as well as X, are located in the Galh region. When S'' and Galb are 

 used as selective markers, the proportion of nonlysogenic recombinants 

 is about 90% with phage 82, 80% with phage X, and 70% with phage 

 434. Prophage 363 is located in a different region. 



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