Chapter 45 



Studies on the Stability of the Na+ 

 Requirement of Marine Bacteria 



Robert A. MacLeod and E. Onofrey 



M. 



.uch information has accumulated indicating a preference 

 of marine bacteria for sea water over fresli water in the medium 

 for growtli. Korinek (2) beheved tliat marine bacteria could be 

 distinguished from non-marine forms on the basis of their 

 salt tolerance. Dianova and Voroshilova (1), using a fish broth 

 medium, obsei'ved that Na" salts were required for the growth 

 of a number of marine isolates and could not be replaced by 

 equimolar concentrations of K^ salts. Zobell and Upham (8) de- 

 fined marine bacteria as bacteria from the sea which on initial 

 isolation require for growth a medium containing sea water as 

 the diluent. In a study of the relation of sea water to the growth 

 of a number of marine bacteria, MacLeod and Onofrey (4) using 

 chemically defined media found that the need for sea water was 

 due to its ability to supply the inorganic ions required for 

 growth by the organisms. A study of the qualitative and the quan- 

 titati\'e requirements of the marine bacteria for inorganic ions re- 

 vealed among other things an almost unique and highly specific 

 requirement for Na^. This requirement for Na^ could not be re- 

 placed in whole or to any significant extent in part, either by any 

 one of a number of related inorganic ions or by organic com- 

 pounds added to increase the osmotic pressure of the medium. It 

 seemed probable that true marine bacteria could best be dis- 

 tinguished from land contaminants present in sea water by the 

 possession of this need for Na*. 



Evidence has been presented which suggests that the re- 

 quirement of marine bacteria for sea water or for Na^ may not be 

 a stable one. Zobell and Michener (7) found that nine of twelve 

 cultures requiring sea water in the medium on initial isolation 



481 



