422 Marine Microbiology 



in the upper part of the phig (S) the production of nitrites and 

 nitrates is clearly more rapid than in the lower portion (P). Let 

 us note at the same time, however, that a very strong nitrifying 

 activity still exists in the deeper layer. 



ANALYSIS OF THE RESULTS OBTAINED 

 ON THE "MATTES" 



These sands covered by vegetation have revealed themselves 

 equally capable to transfomi ammonia into nitrate. If we examine 

 the lag phase of the nitrite curve, we find that these sands have 

 a potential even greater than that of the muds, since the time 

 of latency is nearly always less than fifteen days. 



Similarly, the nitrate curves generally start sooner in the 

 sands than in the muds. 



Now, it is indeed necessary to call attention to the fact that 

 these sands were quite poor in numbers of other bacterial organ- 

 isms. Let us note also that the most active sediment is sand from 

 Castiglione beach. This sample is very poor in innocuous sapro- 

 phytes, and contains no ureolytic flora. We believe it is of interest 

 to compare the results with those we have obtained with some 

 desert sands from Hoggar and Beni-Ounif. These sands, often 

 extremely poor in organic matter and innocuous bacteria, have 

 demonstrated an extremely intense nitrifying activity which is 

 never observed in other soils. 



Halophilic Character of Nitrifying Bacteria 

 in the Studied Marine Sediments 



The results reported above demonstrate the existence, in the 

 marine muds and sands, of a nitrifying microflora whose potential 

 activity is at least equal to that of an average terrestrial soil. But 

 we do not know if this flora is active in situ. In this respect, 

 it seems of interest to compare the behavior of marine strains 

 with those of terrestrial strains in a medium enriched with sodium 

 chloride. ' ' 



Thomsen (5), in 1910, examined Nitwsomonas strains iso- 

 lated from muds of Naples' gulf and Helgoland area. He noted 

 a morphological and physiological identity between these species 

 and the terrestrial strains, but calls attention to the fact that th^ 



