BACTERIOPHAGY IN A FLUID MEDIUM 69 



rather unfavorable to the bacterium involved {B. chjsenteriae Flexner), 

 a complete dissolution of concentrated bacterial suspensions does not 

 take place, it is equally true that bacteriophagy will take place, and in 

 a complete fashion, when the suspension is less heavy, as the following 

 experiments show^''^ (table 8). 



The culture medium is a 1 per cent peptone water, having a pH 

 of 7.0. 



This demonstrates that the bacteriophage is capable of multiplying 

 in media poor in electrolytes, inasmuch as in such media bacteriophagy 

 occurs. 



Brutsaert^^° arrived at the same conclusions, but, according to his 

 observations certain races of the bacteriophage fail to develop under 

 such conditions, while others, on the contrary, are unaffected and lead 

 to a total dissolution of the bacterial cells present in the medium. 



Here again, the same observation is pertinent. It is the quality of 

 the bacteriophage which determines the course of the phenomenon. 



Ciuca^'*^ has also shown that bacteriophagy occurs normally in 

 media poor in electrolytes, provided the active principle operates upon 

 young bacteria. His media were alkaline, pH 7.8 to 8.0. 



In general, then, the conclusions seem to be that in media poor in 

 electrolytes, that is, in salts, bacteriophagy does not take place when 

 the medium is acid. In a neutral medium (pH 7.0) bacteriophagy 

 may or may not occur, depending upon the race of the bacteriophage 

 concerned. In an alkaline medium, the phenomenon takes place with 

 all races; and with the most active the dissolution of the bacteria is 

 complete. 



Instead of considering the effects of deficient quantities of electro- 

 lytes in the medium, the reverse situation offers a problem. What 

 happens when the medium contains a large amount of salt? Bacteri- 

 ophagy takes place normally in bouillon containing 2.5 per cent of salt 

 (d'Herelle^-^) . Brutsaert^"^ has shown that B. coli does not grow in a 

 medium containing more than 5 per cent of NaCl, while staphylococci 

 still develop freely in broth having 14 per cent of salt, yet in such media 

 he observed that bacteriophagy took place normally. According to 

 him, bacteria cultivated in hypertonic bouillon and then placed in 

 contact with the bacteriophage are even more readily attacked than 

 the same bacteria grown in a medium with a normal concentration of 

 salt. 



