90 FRED W. TANNER 



early authors. Ledderhose (1888) believes that this pigment 

 which has been called pyocyanin belongs to a group of aromatic 

 substances closely related to the anthracene group. It was 

 thought that this pigment might be related to anthocyanin 

 which is supposed to have some relation to the flavon or xanthon 

 groups. This may exist in the form of a colorless glucoside in 

 the plant and be capable of oxidation only after it has been 

 Hberated. Repeated tests by Molisch's reaction failed to dem- 

 onstrate its glucosidal character either before or after hydrolysis. 

 More work on this subject is planned. 



Reduction of nitrates 



Nitrate reduction tests were made on media containing dis- 

 tilled water, 1000 cc; Witte's peptone, 1 gram; and potassium 

 nitrate, 2 grams. 



Thirty cubic centimeters of this medium were sterilized in 

 small Erlenmeyer flasks. These were inoculated from a twenty- 

 four-hour broth culture and incubated for five days at 37 °C. 

 At the end of this period 1 cc. of the nitrate broth culture was 

 removed by a sterile pipette and diluted to 50 cc. in a Nessler 

 tube with nitrite free water. 



The method used for determining nitrites was that usually 

 employed in water laboratories, and it is believed that it is not 

 too delicate for bacterial work if blank determinations are made. 

 To each of the Nessler tubes prepared above was added 1 cc. 

 of an acid solution of naphthylamine hydrochloride and 1 cc. of 

 a saturated solution of sulfanilic acid. The tubes were allowed 

 to stand for thirty minutes in the colorimeter before being ex- 

 amined. Control tests were always made at the same time. 



Fifty-one of the strains reduced potassium nitrate when incu- 

 bated for five days at 37°C. 



Formation of ammonia 



The nitrate broth cultures were used for this purpose. At 

 the end of ten days 2 cc. of this broth culture were withdrawn 

 and diluted to 50 cc. with ammonia free water. Nessler's 



