TRANSDUCTION OF LYSOGENY IN ESCHERICHIA COLI 



217 



TABLE 6 

 X-Prophage Recombination through Transduction 



Lysogenic acceptor bacteria P678(Xm5Comi^)+A were infected with phage 363 

 grown on prototrophic lysogenic K12(Xm5'Comi)+. After plating on galactose 

 medium, colonies were reisolated and tested for the type of phage released. 



been replaced by markers of the transduced prophage. In spite of the 

 small numbers involved, it is clear that the markers of the prophage X 

 are not independently substituted, the frequency of substitution de- 

 creasing progressively from the m, to the m^ end of the X linkage group. 



In the second group, corresponding to 9 cases (3.8%), the bacteria 

 were found to release, besides the original msComf type, one or more 

 other types of X particles, even in single-burst experiments. This finding 

 shows that alleles issued from the transduced prophages have been added 

 to the original prophage. Here, again, the mi region is the most fre- 

 quently added. 



These clones, in which bacteria carry two phage alleles at one or 

 several loci, appear to be rather stable, since they were tested for phage 

 production after two successive isolations on agar and growth in broth, 

 corresponding to at least 50 generations. Nevertheless, single-burst ex- 

 periments show that phage markers are very heterogeneously distributed 



349 



