354 Marine Microbiology 



TABLE 2 



The Effect of Volume Filtered on the Percentage Recovery in the 



Filtrate of Various Phages Suspended in Sea Water and Filtered 



Through Cellulose Ester Membrane Filters 



Volume Filtered 

 ml. 

 Phage 20 50 100 200 



Percentage Recovery of Phage 



lose ester membrane filter to remove bacteria and 10 ml samples 

 were mixed with 10 ml of a sea water based nutrient agar (pep- 

 tone 1%, Lab Lemco, 1%, agar 1.5%), melted and cooled to 44 C, 

 together with 2 ml of a young culture of the appropriate bacterial 

 strain, and immediately layered onto the surface of an agar 

 plate of the same composition. After a period of incubation to 

 allow bacterial multiplication to take place, the presence of any 

 phage active against that particular bacterial strain was mani- 

 fested by the appearance of plaques in the depths of the soft 

 agar. Normally, 600 ml amounts of sea water at a time were 

 examined against a total of 40 bacterial cultures with incubation 

 at both C and 20 C. 



A collection of luminous bacteria isolated from the intestines 

 of fish were used in the earlier part of the work, but results with 

 these strains were poor, only one phage being isolated. In the 

 later stages, 40 strains were isolated from sea water and results 

 with these strains were much better, six phages being isolated. 

 Of the seven phages, four were detected by the parallel direct 

 and indirect methods at both 20 C and C. Three of these phages 

 were present in a concentration of one to five particles/10 ml of 

 sea water, and one in a concentration of approximately 100 par- 

 ticles/10 ml. The remaining three phages were detected by the 

 indirect method only where they must have been present in a 

 concentration of at least one particle/300 ml. Table 3 gives 



