208 FRANgOIS JACOB 



This paper is mainly concerned with preliminary results on trans- 

 duction of lysogeny in E. coli K12 by the use of a strain of temperate 

 phage isolated in our laboratory. Previously, information on the genetics 

 of X lysogeny was gained through bacterial recombination experiments 

 with E. coli K12 (Lederberg and Lederberg, 1953; Wollman, 1953; 

 Appleyard, 1954a; Wollman and Jacob, 1954). The results indicated 

 that the X-lysogenic character segregates in crosses between lysogenic 

 and nonlysogenic bacteria and, moreover, that this character is linked 

 to a marker that plays a role in galactose utilization. Nevertheless, 

 whereas the presence of a nuclear unit controlling lysogeny was thus 

 demonstrated, it had not yet been proved fully that this bacterial unit 

 was identical to the prophage, i.e., to the genetic material of the phage 

 in the lysogenic condition (Lwoff, 1953). Transduction of lysogeny offers 

 a new way of analyzing the relations between prophage and bacterium, 

 as well as the size and orientation of the prophage. 



MATERIAL AND METHODS 



Transducing phage. Various kinds of temperate phages have been 

 tested for their transducing ability in E. coli K12. Of twenty-three 

 phages released by difTerent lysogenic strains of E. coli isolated from 

 patients, only one was active: phage 363. It forms tiny turbid plaques 

 on E. coli K12 (Fig. lA). Its latent period in broth is about 50 minutes, 

 and its burst size is 200 to 300. Its frequency of lysogenization is higher 

 at 20° than at 37°. Phage 363 appears to belong to the same group as 

 phage PI, previously described by Bertani and Nice (1954) and used 

 by Lennox (1955) in his transduction experiments. Bacteria lysogenic 

 for 363 are immune against PI, and vice versa. Phage 363 is inactivated, 

 although at a lower rate than PI, by an anti-Pl serum. ^ 



Transduced prophage. The properties of phage X and its relationship 

 with the bacterial host have been described (Lederberg and Lederberg, 

 1953; Weigle and Delbriick, 1951). Two other temperate and ultraviolet- 

 inducible phages, released by lysogenic E. coli isolated from patients, 

 have also been used in these experiments: phages 82 and 434 (Fig. IB, D). 

 The properties of these two phages will be described elsewhere. Phages 

 82, X, and 434 can easily be distinguished by their host range, as shown 

 in Table 1. 



Bacterial strains. The bacterial strain used as a donor was a proto- 

 troph, K12, sensitive to 363, 82, X, and 434. 



' A sample of anti PI serum (anti H~) was kindly supplied by Dr. J. Beumer. 



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