SCIENTIFIC PROCEEDINGS 



Abstracts of Communications. 



One hundred thirtieth meeting. 



Rockefeller Institute, New York City, March 21, 1923. 

 President Wallace in the chair. 



148 (2108) 



Food accessory substances and the nitrite bacteria. 



By T. J. MURRAY. 



[From the Department of Bacteriology, Rutgers College, New 

 Brunswick, N. J.] 



In the isolation of nitrifying bacteria, soil is inoculated into a 

 synthetic solution containing (NH 4 ) 2 S0 4 as a source of nitrogen 

 for the "nitrite" bacteria and into one containing NaN0 2 for the 

 "nitrate" bacteria. The solutions are incubated and when a test 

 for nitrites is found in one case or a test for nitrates in the other, 

 a small amount of the liquid is transferred to a new synthetic 

 solution. This transferring is continued for some time. Then 

 the material is plated out on silica jelly containing suitable in- 

 organic salts. From the colonies developing, inoculations are 

 made into synthetic solution and if nitrites are formed in the one 

 containing (NH 4 ) 2 S0 4 a "nitrite" bacteria has been isolated or 

 if nitrates are formed where NaN0 2 is the source of nitrogen a 

 "nitrate" bacteria has been isolated. 



Great difficulty was experienced in isolating cultures by the 

 above procedure. At the beginning, in no case where inoculations 

 from the colonies on silica jelly were made into the synthetic 

 solution, were positive tests subsequently obtained. If, however, 

 a solution giving a positive test were centrifuged and the sedi- 



