Bacterial Viruses in the Sea 363 



medium without the addition of NaCl would. It was also found 

 that if the bacterial cells used to inoculate the surface of the 

 agar medium were not washed free from salts, lysis could on 

 occasions take place up to a NaCl concentration of 0.4 M. The 

 addition of MgCL in 0.1 or 0.2 M concentration would uniformly 

 allow lysis to take place up to a NaCl concentration of at least 

 0.6 M. These preliminary results are interpreted as indicating 

 that once again both NaCl and MgClj are required for lysis but 

 that a balance is required. If the balance is destroyed by the 

 presence of too much NaCl, lysis will not take place. Conversely, 

 if the concentrations of the two salts are balanced, lysis will take 

 place even at very low total concentrations of salts. It has also 

 been shown that MgSOi and CaCL can replace MgCb, and that 

 KCl and Na2S04 can destroy the balance. It would thus appear 

 that this balance is essentially a monovalent/divalent cation 

 balance. 



Phage P/SWl/b. It should be noted firstly that phage 

 P/SWl/a, isolated against the same host organism, causes lysis 

 quite well on the tap water media. TJie requirement of P/SWl/b 

 for a sea water based medium has not yet been investigated in 

 any detail but the nature of the requirements appear to differ 

 from those of P/14 and P/L/34. 



The requirement of many phages for cations for adsorption 

 to and thus lysis of the host bacterium is well known (2). Ca^^ 

 in particular is frequently required but univalent cations such 

 as Na"^ may also be necessary. The concentrations of the cations 

 required, for example 0.01 M for univalent and 0.001 M for 

 divalent cations for phage Tl (14) or 0.014-0.06 M for mono- 

 valent cations and approximately a tenth of these values for 

 divalent cations for adsorption of a Shigella dysenteriae phage 

 (4), were, however, much lower than those required for P/14. 

 The apparent requirement of P/L/34 for a cationic balance, even 

 at high cation concentrations, does not seem to have been met 

 with in the case of terrestrial phages. It has been shown that 

 certain marine bacteria have a positive requirement for Na^ 

 (13), which again has not been met with in the case of terrestrial 

 bacteria, and it may be tliat with both bacteria and phages, an 



