CHAPTER V 



EFFECTS OF PHYSICAL AND CHEMICAL 



AGENTS (EXCEPT RADIATIONS) 



ON BACTERIOPHAGE PARTICLES 



The commonly studied bacteriophages are extraordinarily 

 stable under appropriate conditions. The infective titer may 

 fall at the rate of one per cent per day, or often much less. 

 Needless to say, the stability depends on many environmental 

 factors, some of which act differently on different phages. A 

 knowledge of these factors is of immediate concern to anyone 

 interested in the concentration, purification, or preservation of 

 phage. 



Phages are generally stable in their own lysates provided these 

 are free from specific inactivating agents (receptor substances) 

 derived from the lysed bacteria, and contain suitable electro- 

 lytes. The absence of general poisons is more or less guaranteed 

 by the fact that the phage grew in the first place. Purified 

 phages are generally stable in neutral, buffered solutions, pre- 

 pared from glass-distilled water, containing 0.1 M sodium 

 chloride, 0.001 M magnesium chloride, and, if the phage con- 

 centration is low, a small amount of gelatin. The effects of 

 receptor substances, if these are not completely removed, can be 

 minimized by choosing conditions unfavorable for specific 

 interaction, but these conditions vary greatly from phage to 

 phage. Low temperatures, of course, favor stability, especially 

 if other conditions are suboptimal. 



In addition to these purely practical considerations, the study 

 of inactivation of phages under controlled conditions has yielded 

 important information about the structure and function of 

 phage particles. Much of the recent systematic work has dealt 



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