392 BACTERIOPHAGES 



5. Bacteriocins and Bacteriophages 



Analogy between phages and bacteriocins, first pointed out by 

 Gratia (1925, 1932), was later emphasized by almost every 

 worker in the field. Properties of phages and bacteriocins may 

 be compared at two different levels. 



7. The action of phages and of bacteriocins on susceptible 

 cells is similar in many respects. Both agents are adsorbed on 

 specific receptors which, in some instances, may even be common 

 for phages and bacteriocins. The loss of receptors by bacterial 

 mutation results in resistance to the agent. Adsorption of a 

 single particle of either one appears to be sufl^cient to kill a cell. 

 Finally, bacteriocins interfere with the metabolism of susceptible 

 cells as strongly as virulent phages like T2 (Fredericq, 1953; 

 Jacob, Siminovitch, and Wollman, 1953). 



2. The capacity to produce temperate phages or bacteriocins 

 is a genetic character perpetuated as a potential property the ex- 

 pression of which is lethal. In certain examples of both sys- 

 tems, the lethal biosynthesis can be induced by similar experi- 

 mental procedures in the whole population (Jacob, Siminovitch, 

 and Wollman, 1953). 



In their adsorption specificity and mode of action bacteriocins 

 can best be compared to the proteinaceous "ghosts" obtained 

 by subjecting phage T2 to osmotic shock. Colicin K and phage 

 T6 adsorb on the same bacterial receptors. The killing abilities of 

 these two agents are destroyed at similar rates by X-rays (Latar- 

 jet and Fredericq, 1955), a result which would suggest that the 

 colicin and the protein of the tip of the tail of the phage might 

 be similar in nature and size. These two proteins are antigeni- 

 cally unrelated (Goebel, Barry, .Tesaitis, and Miller, 1955), but so 

 are, in general, different phages like Tl and T5 which may nev- 

 ertheless adsorb to the same receptors. 



Although bacteriocins and bacteriophages lend themselves to 

 obvious comparisons, there is no indication for the existence of 

 any direct relationship between these two groups of antibacterial 

 agents, such as a colicin being the product of an incomplete 

 phage development. In particular no case has been as yet 



