CHAPTER XVII 



CHROMOGENIC BACTERIA 



Introduction. Some species of bacteria when growing in 

 cultures exhibit various colors. Bacteria of this character are 

 called chromogenic. 



The majority of bacteria produce no color whatever and 

 appear white or colorless when growing in cultures. They are 

 called non-chromo genie. 



Range of Color. The chromogenic bacteria present, in the 

 various species, all the colors of the solar spectrum. The 

 following table gives the colors of the spectrum and an example 

 of a chromogenic bacterium which will normally produce prac- 

 tically the corresponding color in cultures. 



Red Bacillus prodigiosus Fliigge 



Orange Sarcina aurantiaca Fliigge 



Yellow Micrococcus flavus Fliigge 



Green Bacterium viridis Kruse 



Blue Pseudomonas syncyanea Migula 



Indigo Pseudomonas indigofera Voges 



Violet Bacillus violaceous Jordan 



There are also species of bacteria which produce all the 

 shades between the various colors of the spectrum. 



The color of chromogenic bacteria is due to pigment 

 granules. The position of the pigment granules in relation to 



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