Bacterial Viruses in the Sea 353 



TABLE 1 



The Effect on Phage Titre of Shaking Suspensions of Various Phages 

 WITH Certain Organic Solvents (10 ml. of Phage Suspension Were 

 Shaken with 0.1 ml. of Solvent for One Minute Followed by Five Min- 

 utes Standing Before Sampling). 



The figures in parenthesis show the number of replicate experiments of which 

 the titre given is the mean. 

 ^ anti-Staphylococcus aureus phage 

 - ant'i-Escherichia coli phage 

 3 anU-Bacillus mycoides phage 



Wliere a phage was isolated, the four cultures were tested against 

 one another for lysogenicity; with negative results. 



The aim of the direct method for phage isolation was not 

 only to isolate phages, but also to measure their concentrations 

 against any particular host organisms, and consequently the 

 standard soft agar layer method for phage assay was adapted to 

 this purpose. To avoid interference by colonies developing from 

 bacteria in the sea water, it was necessary to remove completely 

 all such bacteria without affecting the phage concentration. Cellu- 

 lose ester membrane filters were used for this purpose as it 

 was found that \irtually complete recovery of certain terrestrial 

 and marine phages suspended in sea water was possible, pro- 

 vided more than 200 ml of the suspension were passed through 

 tlie filter. Table 2. 



In the direct method, sea water was passed through a cellu- 



