Makch 6, 1903.] 



SCIENCE. 



371 



bacteria are those that grow in nitrogen- 

 free or nitrogen-poor media, and that pos- 

 sess the power of utilizing the free nitrogen 

 of the air. The oligonitrophiles belong 

 to the Clostridium group, or to Beijerinek's 

 Granulobacter group. 



Clostridium Pasteurianum, Avhich AVino- 

 gradsky found to possess nitrogen-assimi- 

 lating properties, is an anaerobe, but it 

 also grows in symbiosis with aerobic forms ; 

 it is, therefore microaerophilic. The miero- 

 aerophiles will grow luxuriantly under 

 normal conditions under diminished ox- 

 ygen pressui'e, effected by the active utili- 

 zation of oxygen by the aerobes (macro- 

 aerophiles). 



Nitrogen assimilation in the soil is not 

 the result of the activities of a single oi'- 

 ganism, but of symbiosis of microaerophiles 

 with macroaerophiles. Of the micro- 

 aerophiles we have Clostridium Pasteur- 

 ianum, several species of Granulobacter of 

 Beijerinck, and Radiobactcr of Beijerinck. 

 Of the macroaerophiles we have Azoto- 

 bacter of Beijerinck. 



Azotobacter alone is without nitrogen- 

 assimilating properties, and the same is 

 true of the Granulobacter and Radiobacter, 

 but mixed cultures of Azotobacter Avith the 

 other forms showed marked gain of nitro- 

 gen of four to seven milligrams per gram 

 of assimilated sugar in the medium. A 

 form of Azotobacter isolated from Dela- 

 ware soil was without the power of assimi- 

 lating atmospheric nitrogen. 



The Bacterial Flora of the Oyster's Intes- 

 tine: Caleb A. Fuller, Brown Univer- 

 sity. 



Of late there has been considerable dif- 

 ference of opinion regarding the signifi- 

 cance of B. coli in drinking water and 

 various foodstuff's. Some authorities do 

 not consider this organism a certain indica- 

 tion of sewage pollution, while others look 



with suspicion on all food materials con- 

 taining bacteria of the colon group. 

 Oysters are especially liable to contamina- 

 tion by sewage, for many cities and towns 

 discharge their waste matters into bays or 

 other bodies of water where they are cul- 

 tivated. 



In some reports on the bacteriology of 

 the oyster it was suggested that B. coli 

 might be present normally in the intestines 

 of oysters. This statement differs mate- 

 rially from the results of some previous 

 work of mine on oysters and sewage in 

 Narragansett Bay. These results seem to 

 indicate that this organism does not occur 

 in oysters obtained from perfectly clean 

 sea-water. In order to throw some light 

 on this point I examined the intestines of 

 over two hundred oysters in October and 

 November, 1902. These oysters were taken 

 from a bed Imown to be free from any trace 

 of sewage. A number of tests have shown 

 that the sea-water above this bed does not 

 contain B. coli. 



The method of analysis was as follows: 

 Two gelatin plates were inoculated, each 

 Avith a large loop of material from the in- 

 testine of each oyster and grown at room 

 temperature for three or four days. One 

 of these plates was made from the usual 

 nutrient gelatin and the second from 

 gelatin containing carbolic acid (.05 per 

 cent.). Prom the ordinary gelatin plates 

 I separated sixteen species of bacteria; 

 some of them common Avater forms, and 

 others unidentified, that seem to be char- 

 acteristic of the oysters of this locality. Of 

 the carbol-gelatin plates, with but a single 

 exception all remained sterile. The single 

 colony that developed was not B. coli. If 

 B. coli was present in the intestines of these 

 oysters, even in small numbers, it would 

 have developed in the above medium. Of 

 the other species isolated, none resembled 

 B. coli when tested by the usual methods. 



