84 Marine Microbiology 



SUMMARY 



Nitrification and the presence of nitrifying bacteria were 

 demonstrated in Atlantic oceanic waters collected from the con- 

 tinental shelf and the Sargasso Sea. These nitrifying microorgan- 

 isms have been maintained in reproducible laboratory culture by 

 periodic subculture for eighteen months. Although morphologic- 

 alh' different from any described species of Nitrosomonas or 

 Nitrobacter, they are physiologically similar to known strains of 

 Nitrosomonas europaea and Nitrobacter agilis. The one distin- 

 guishing physiological difference between terrestrial and marine 

 forms is their response to NaCl. Both terrestrial and marine forms 

 grew for a limited period in the presence or absence of NaCl, 

 but the terrestrial bacteria did best in the absence of NaCl and 

 the marine fomis did best in a medium with 2.5 per cent NaCl. 

 These preliminary studies indicate that there are populations of 

 oceanic nitrifying microorganisms within the water column. 



ACKNOWLEDGMENTS 



I wish to thank Dr. John Kanwisher for his generous help 

 in using the oxygen electrode and Mr. Charles Yentsch who 

 kindly made the measurements with the Carey Recording Spectro- 

 photometer. 



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