LYSOGENY 377 



material of bacterial origin from one bacterium to another. On 

 the other hand, in certain systems, specific alterations of bacterial 

 properties by lysogenization have been reported which appear 

 to be so entangled with the lysogenic character that they can 

 be ascribed to the very presence of a prophage. 



a. Transduction 



Certain strains of temperate phages are able to carry a piece 

 of genetic material from a donor bacterium, on which the phages 

 have multiplied, to a recipient bacterium which they infect 

 (Zinder and Lederberg, 1952; Zinder, 1953). Among the 

 recipient cells surviving the infection, some have acquired new 

 genetic properties originating in the donor bacterium. 



In many cases transduction is not specific and any character 

 of the donor may be transmitted with an equal and low (10~^ 

 or 10~^) probability. Everything appears as if the genetic 

 material of the donor was disrupted during the multiplication of 

 the phage permitting segments of this material to be incorporated 

 by chance into occasional phage particles. 



Such nonspecific transduction is observed in Salmonella (Zinder 

 and Lederberg, 1952) and in E. coli (Lennox, 1955). When 

 characters are closely linked, they may be transduced together 

 (Stocker, Zinder, and Lederberg, 1953; Lennox, 1955) and 

 this possibility has been systematically used for genetic analysis 

 of small chromosomal segments of bacteria (Demerec and Dem- 

 erec 1956). 



Among the characters which can thus be transduced from 

 donor to recipient bacteria is the lysogenic character itself. 

 A phage particle acting as a vector may carry, in addition to 

 its own genetic material, a piece of bacterial chromosome carry- 

 ing one or even more unrelated prophages (Jacob, 1955). In 

 other words, a phage coat may contain the genetic information 

 necessary for the synthesis of two or even three different phages. 



Another type of phage-mediated transfer of genetic characters 

 has been recently described in phage lambda (Morse, Leder- 

 berg, and Lederberg, 1956). This transduction appears to be 



