142 MICROBIOLOGY 



(1) Red and yellow pigments. Schneider studied twenty- 

 seven red and yellow pigment forming bacteria, nearly all of 

 which produced coloring matter soluble in alcohol and in- 

 soluble in water. The larger majority of them were colored 

 blue-green with sulphuric acid and red or orange with a solu- 

 tion of potash. They varied in their chemical composition 

 and in their spectra. They may be classified, for the most 

 part, among that large group of pigments common to both 

 the animal and vegetable kingdoms known as lipochromes, 

 and to which belong the pigments of fat, yolk of egg, the 

 carotin of carrots, turnips, etc. (2) Violet pigments. Cer- 

 tain bacteria produce violet pigments, insoluble in water, 

 ether, benzol and chloroform, but soluble in alcohol. (3) Blue 

 pigments. Ps. pyocyaneus produces the blue pyocyanin. It 

 is stated that it is also produced by the so-called fluorescent 

 bacteria, along with a pigment named bacteriofluorescein. In 

 cultures, the fluorescence is at first blue ; later, as the cultures 

 become alkaline, it is green. (4) Fluorescent pigments. The 

 fluorescent pigments which occur in the cultures of very 

 many bacteria are identical, according to the recent investi- 

 gations of K. Thumm. 1 The pigment which is called bacterio- 

 fluorescein, when dry, is lemon-yellow and amorphous. It is 

 soluble in water and dilute alcohol, insoluble in strong alcohol, 

 ether, and carbon bisulphid. The aqueous solution of this 

 pigment, when concentrated, is orange ; when diluted, pale 

 yellow*. The solution, when acid in reaction, presents no 

 fluorescence ; when neutral, a blue ; and when alkaline, a green 

 fluorescence. In the culture the fluorescence is at first blue, 

 and later, because of the ammonia produced by the bacteria, 

 it becomes green. The pigment is not sensitive to oxidizing 

 agents. Phosphoric acid and magnesium appear to be essen- 

 tial for the production of bacteriofluorescein. 2 



The beautiful blue crystalline pigment, pyocyanin, 

 C 14 H 14 O, can be easily extracted from cultures of Ps. pyo- 



1 Thumm. Arbeiten aus dem bakteriologischen Institut der 

 techn. Hochschule zu Karlsruhe, Bd. I, p. 291. 



2 Jordan. Botanical Gazette, Vol. XXVII, p. 19. 



