Proteolysis and Nitrate Reduction in Sea Water 411 



is 3.3 Gm (%) and equivalent to NaCl concentration in sea water. 



The isolations have been made on a medium prepared with 

 natural sea water, flesh of fishes or shellfish, 1 per cent lactose, 

 0.05% 2-4-diphenyl tetrazolium, and bromthymol blue; pH ad- 

 justed to 7.3. The cultures have been incubated at 25C for twenty- 

 four hours. This routine technique provides a rapid isolation of 

 several different species from a single inoculated specimen (sea 

 water, mud, intestinal tract of fishes, etc.). 



After isolation and purification, the strains have been identi- 

 fied by our routine techniques (sugar fermentations, protein 

 metabolism, organic acid production, etc.) and finally all the 

 strains were tested for agglutination with Achromohacter and 

 Envinia anti-sera. The identifications have been made according 

 to the French classifications of Magrou and Prevot (8) and 

 Brisou (1). 



Proteolysis has been tested at 22 C and pH 7.3 with: (1) 

 15% gelatin stab and with: (2) 1% peptone water added with 

 a small piece of gelatin according to the technique of Kohn. 



Nitrate reduction was tested in peptone water containing 

 1% potassium nitrate, and nitiite formation was characterized 

 by the Griess reaction after 48 hours of incubation at 25 C. 



For the halophilic bacteria, the media were prepared with 

 natural sea water. 



RESULTS 



For a total of 131 strains investigated, 77 are proteolytic and 

 77 nitrate reducing; 51 strains have both these activities; 26 

 strains are inactive. 



The separation of these strains in the different genera is as 

 follows : 

 Vibrios 



All the 13 strains of Vibrio isolated are strictly halophilic. 

 Origins: salt lake of Sahara and Atlantic Oceans (Cap Ferret 

 beach ) . 



