Micro-organisms of Maw.f. Sap 



543 



TABLE 58. AM \ln\iA PBODT ( TION 



3. Action on nitrates. — Nitrates in nitrate broth were re- 

 duced to nitrites by three strains, as indicated by the iodo 

 starch reaction (27:63). All cultures showed ammonia with 

 Nessler's reagent ; but this was thought to have been an end 

 product of proteid decomposition rather than of nitrate reduc- 

 tion. No gas was produced. 



Two formulas for nitrate broth were used with similar re- 

 sults. 



I. Distilled water 1000. cc. 



Liebig's extract of meat ::. 



Witte's peptone 10. gr. 



Potassium nitrate :!. gr. 



II. Distilled water 1000. cc. 



Witte's peptone 1. gr. 



Potassium nitrate 2. gr. 



Cultures in media of the first type were tested at the end 

 of 10 days and 30 days. Only strain LI responded with a posi- 

 tive reaction at the first test, but strains LI, LIV, and XXXVI 

 showed prompt blackening when tested after 30 days. The 

 reaction was more rapid in media prepared by formula If and 

 a positive reaction was obtained in 5 day old cultures of strains 

 LI, LIV and XXXVI. Only these three strains showed the 

 presence of nitrites at any time on either medium. The te I 



