TRANSDUCTION OF LYSOGENY IN ESCHERICHIA COLI 211 



TABLE 2 

 Transduction of Various Markers with Phage 363 



nor 's ft"v^i ns Colonies per 5.6 X W 



Selection for '^.tninflrt J bacteria infected with 



bacteda 1.2 X 10« phage 363 



Threonine"'" 



Leucine"*" 



Threonine"*" + leucine^ 



Lactose"*^ 



Galactoseb 



Acceptor P678 bacteria infected with phage 363 grown on prototrophic K12 

 (multiplicity of infection, 0.3), and uninfected control bacteria were shaken for 

 2 hours at room temperature. After centrifugation, the bacteria were resus- 

 pended in buffer and plated on various selective media. 



duced. Aliquots of noninfected P678 bacteria and of bacteria infected 

 with phage 363 grown on a prototrophic strain were plated on various 

 selective media. It is seen in Table 2 that the nutritional characters 

 threonine^ or leucine"+^ are transferred separately with a frequency of 

 about 10~^ per adsorbed particle. These two markers, which are known 

 to be linked from bacterial recombination experiments (Lederberg, 

 1947), can be transferred simultaneously with a frequency of about 10^'' 

 per phage particle. 



The two fermentative markers, Lac^ and Gait, are transmitted with 

 a lower efficiency than T^ or L+. Gait, with which the experiments re- 

 ported in this paper will be mainly concerned, is transferred with a fre- 

 quency of about 0.7 to 1.5 X 10~^ per phage particle. Four hundred 

 colonies selected for transduction of Gait were assayed for threonine, 

 leucine, lactose, mannitol, and xylose. None of them had acquired any 

 of these characters other than galactose utilization. 



The efficiency of transduction varied widely from one experiment to 

 another and from one preparation of phage 363 to another. In various 

 experiments, the frequency of lysogenization with phage 363 in the 

 transduced clones was found to vary from 30 to 70%. Nevertheless, 

 in a given experiment, this proportion was about the same for each class 

 of transduced cells, independently of the selective marker. 



Transfer of nonlysogeny. In order to demonstrate transfer of non- 

 lysogeny, bacteria lysogenic for one of the three prophages — 82, X, or 

 434 — and resistant (nonabsorber) to the homologous phage were infected 



343 



