Genetics 



T+ L+ S"^ does not exceed 5% of the initial number of Hfr bacteria, 

 although more than 50% of these bacteria give rise to infective centers. 

 Among 200 recombinants examined not one was lysogenic. In a compar- 

 able cross in which the F~ strain perpetuates a defective prophage, the 

 number of T+ L"*" S"" recombinants reaches 50% of the initial number of 

 Hfr, although the number of infective centers does not surpass 5%. 

 Among the recombinants about 30% are normal lysogenics. 



The phenomenon of spontaneous induction of the prophage is also found 

 in crosses of F+ ly+ by F~ ly~ and thus explains the observed absence 

 of the transmission of lysogeny in these crosses. It could also be the origin 

 of other anomalies found in the study of the genetics of E. coli K12. 



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