GENUS PSEUDOMONAS 357 



Cultivation. Pseudomonas pyocyaneus grows readily on 

 the ordinary cultural media at the body temperature. 



Agar. On the surface of agar a wrinkled, moist, slightly 

 greenish- white layer is developed within 24 to 48 hours, while 

 the medium itself becomes bright green. Later the color be- 

 comes much darker and is changed to a bluish green or almost 

 black color. 



Gelatin. In gelatin this organism develops colonies quite 

 rapidly. The medium becomes a fluorescent green in color. 

 The gelatin begins to liquefy in from 2 to 3 days and by the 

 end of a week it is usually entirely liquefied. The surface 

 colonies have a dark greenish center surrounded by a more 

 delicate radiating zone. In stick cultures liquefaction begins 

 at the surface in the form of a funnel and gradually extends 

 downward. Later the liquid gelatin is separated from the 

 solid by a horizontal plane. The gelatin near the surface has 

 a greenish-yellow color. 



Potato. On potato, a rusty brown growth appears, which 

 is usually profuse. This changes later from a brown to a green 

 color after lightly touching it. This has been referred to by 

 Paul Ernst as the chameleon phenomenon. 



Bouillon. This medium becomes a greenish color, espe- 

 cially near the surface. The growth appears as a more or less 

 flocculent sediment. This medium gives off a peculiar sweetish 

 odor.* In bouillon containing glucose, lactose or saccharose, 

 the liquid becomes more alkaline and no gas is formed. 



Milk. Milk becomes yellowish green in color. The casein 

 is precipitated. In old cultures the casein may be digested. 



Life conditions and properties. Pseudomonas pyocyaneus 

 is an aerobe. In the presence of air it grows on the ordinary 

 culture media at a temperature of from 20 to 37 C. The 

 blood temperature is more favorable. It liquefies gelatin and 

 produces a very pronounced pigment. In old cultures this 



* Because of this odor Sternberg designated this organism the 

 "honey bacillus" in his report on yellow fever. The odor appears in 

 cultures on all the media but it seems to be more pronounced in 

 bouillon. 



