286 BACTERIOPHAGES 



diamidines and the acridines. Indeed, an acridine-like effect is 

 suggested by the fact that propamidine yields sterile lysates of 

 T2-infected bacteria (Bourke, Robbins, and Smith, 1952). 



c. Dyestujfs 



Antiseptic dyes usually inactivate free phage particles. The 

 inactivation may be direct or, as in the case of methylene blue, 

 it may require the participation of light and oxidizable sub- 

 strates. In a few cases, however, dyes have been shown to 

 differentially inhibit phage production without affecting the 

 activity of the free phage. Most notable of these include crystal 

 violet (Graham and Nelson, 1 954) and malachite green (Wolff and 

 Janzen, 1922; Fitzgerald and Babbitt, 1946; Czekalowski, 

 1952). 



7. Summary 



Phage production can be prevented by a wide variety of 

 chemical inhibitors. These may inhibit phage formation only 

 or, if the reactions which they affect are also required for host 

 metabolism, they may also inhibit the growth of uninfected bac- 

 teria. Infection can be prevented by interfering with the 

 adsorption or penetration processes. Prevention of adsorption 

 can be obtained by destroying the organ of attachment of the 

 phage with strong oxidizing agents or metal-cyanide complexes, 

 by destroying the complementary receptor sites of the host by a 

 variety of chemical treatments, or by interference at the level of 

 cofactor requirements for adsorption. Penetration may be 

 prevented by chelating agents, or by inactivating a structure 

 in the phage, presumably an enzyme, necessary for the injection 

 of DNA into the host. The synthesis of protein and nucleic acid 

 may be inhibited by numerous agents which include respiratory 

 poisons, specific inhibitors of protein synthesis, and analogues of 

 amino acids, purines, pyrimidines, and vitamins. In the known 

 cases, any interference with protein and nucleic acid synthesis 

 prevents not only phage production, but also multiplication of 

 uninfected bacteria. 



