210 FRANgOIS JACOB 



TABLE 1 

 Host Range of Phages 82, X, and 434 



Media. For infection experiments, broth supplemented with 10~^ M 

 CaCU was used. 



The selective medium was the following: KH2PO4 — 13.6 g; (NH4)2S04 

 — 2 g; Ca (NOOz— 0.001 g; MgS04-7 H2O— 0.02 g; Difco agar— 20 g; 

 H2O — 1000 ml; KOH added to pH 7.0. Sugars were added separately at 

 a concentration of 1 %. Amino acids were added at a concentration of 

 100 Mg/ml; vitamin Bi at 5 Mg/ml. 



Transduction experiments. Phage 363 was grown on the prototroph 

 strain K12, either lysogenic or not. The preparations were sterilized 

 with chloroform. Their titer usually reached between 2 and 8 X 10^ 

 particles per milliliter. 



For transduction experiments, about 5 X 10^ particles of phage 363 

 were added to 4 ml of a broth culture containing about 2X10^ bacteria 

 per milliliter of the acceptor strain, P678 aS''. This mixture was shaken 

 for 2 hours at room temperature and then centrifuged and washed. The 

 bacterial pellet was resuspended in buffer, and aliquots were plated on 

 selective minimal medium supplemented with streptomycin to avoid 

 contamination. In each experiment, the phage preparation was tested 

 for sterility as well as for plaque count, and a noninfected culture was 

 assayed as a control for spontaneous mutants. 



EXPERIMENTAL RESULTS 



Evidence for transfer of bacterial genetic material through phage 363. 

 Phage 363 can transfer various kinds of characters from donor to ac- 

 ceptor cells. As previously found by Lennox (1955), unlinked characters 

 are transduced independently, whereas characters which are known to 

 be hnked can be transduced simultaneously. In Table 2 are reported 

 the results of an experiment in which several characters have been trans- 



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