GENETICS 



SPONTANEOUS INDUCTION OF THE DEVELOPMENT 



OF BACTERIOPHAGE X IN GENETIC RECOMBINATION OF 



ESCHERICHIA CO LI K12 



by 



Frangois Jacob and Elie WoUman 



Transmitted by Jacques Trefouel 



In the course of crosses between lysogenic Hfr and non-lysogenic F" 

 bacteria of E. coli K12, the prophage passes from the lysogenic to the non- 

 lysogenic parent becomes induced, and develops in the latter. This process 

 leads to the destruction of the zygote formed. 



In crosses between lysogenic (ly"*") and non-lysogenic (ly~) Escherichia 

 coli K12 we have not been able to demonstrate the transfer of the lysogeny 

 of the F+ parent to a recombinant possessing essentially F~ genome.^ 

 Nevertheless, the lysogenic character segregated and appeared to be linked 

 to another genetic factor. '^> ^ Since the X prophage is inducible, it appeared 

 possible that recombination between F+ly+ and F~ly" involves the 

 development of the phage and the destruction of the zygotes formed' 

 The discovery of strains giving a high frequency of recombination (Hfr)' 

 makes it possible to verify this hypothesis. 



Hfr ly+ S^ bacteria (lysogenic and sensitive to streptomycin) and F~ 

 ly"/X S'' bacteria (non-lysogenic and resistant to X and to streptomycin) 

 are mixed in broth in the proportion of 1 Hfr to 20 F~ . This mixture is 

 shaken at 37° and at various times samples are removed and spread on strep- 

 tomycin containing agar seeded with indicator bacteria resistant to strep- 

 tomycin but sensitive to phage X. A control culture of Hfr is treated in the same 

 manner. 



One observes that the number of infective centers in the mixture in- 

 creases linearly as a function of time until about the 40th minute, when a 

 plateau is reached which corresponds to approximately half of the initial 



IE. L. Wollman, Ann. Inst. Pasteur, 84, 281, (1953). 

 2E. M. and J. Lederberg, Genetics, 38, 51, (1953). 



3L. L. Cavalli and H. Heslot, Nature, 164, 1057, (1949); W. Hayes, Cold Spring Harb. 

 Symp. 18, 75, (1953); W. Haj'es has sent us his strains of Hfr. 



Translated from the French and reprinted by permission of the 



authors and the Imprim^rie Gauthier-Villars from the Comptes 



Rendus des Seances de l'Academie des Sciences, 239, 



317-319 (1954). 



336 



