630 Marine Microbiology 



which might be masked by inhibitions at higher concentrations. 

 The results reported in this paper are consistent with the view 

 expressed by Richter in 1928 ( quoted by Flannery ( 1 ) ) , that Na"^ 

 satisfies both a specific nutritional function and a non-specific os- 

 motic function in the growth of marine bacteria. 



METHODS 



The organism employed was previously described under the 

 designation MB 22 (8, 10). It was a gram-negative, polarly 

 flagellated rod, which produced acid anaerobically from glucose, 

 formed indole from tryptophan, and nitrite from nitrate. The cells 

 were curved in older cultures, particularly in sohd media. This 

 isolate has been tentatively considered to belong to the genus 

 Vibrio and has been designated Vibrio MB 22. Preliminary ex- 

 periments were also made using three other marine isolates: MB 

 1, MB 21, and MB 29 (10). 



The procedure was to study the effect of solute concentra- 

 tion on the growth rate and total growth in a basal medium con- 

 sisting of 0.1 per cent trypticase (BBL), 0.05 M MgCb, 0.005 M 

 K0SO4 and 0.0003 per cent FeS04:7H.O. The medium was ad- 

 justed to pH 7 with dilute KOH. This medium containing 0.4 M 

 NaCl was used to grow inocula; the inoculum cultures were 

 centrifuged and resuspended in a salt solution containing 0.4 M 

 NaCl, 0.05 MgCL, and 0.005 M K,SO.. The cell density of the 

 inoculum was adjusted so that a one hundred fold dilution in 

 the trial medium had a slight turbidity; the cell density after 

 dilution was approximately 10^ cells per ml. The introduction of 

 salts from the inoculum was minimized by dilution and made no 

 significant contribution to the osmotic activitv of the medium. 

 The volume of medium was 20 ml; the inoculum size was 0.2 ml; 

 and the incubation temperature was 32 C. The cultures were 

 grown in 250 ml Erlenmeyer flasks with an attached colorimeter 

 tube and shaken constantly during incubation; the turbidities of 

 the cultures were measured periodically. For the purpose of 

 clarity in presenting results, growth rate was determined during 

 five hours incubation. Examination of individual growth curves 

 demonstrated that differences in growth lag did not make a ma- 



