CHROMOGENIC BACTERIA IQI 



the cell is important. It has been found that there is a great 

 variation among different species in this particular. 



Location of Pigments. In the cultures of some species of 

 bacteria the pigment granules can be seen outside the bacteria, 

 between the cells. In cultures of Bacillus prodigiosus, Pseudo- 

 monas indigofera, and the large majority of the chromogenic 

 bacteria this condition is noted. Those bacteria which ex- 

 crete their pigment are called chromoparous. 



There are other chromogenic bacteria which do not excrete 

 the pigment granules but retain them within the cell proto- 

 plasm. These bacteria are called chromatophorous. The 

 pigment granules are found to be most abundant in the outer 

 layers of the cell protoplasm. A large number of species 

 among the higher bacteria, as, for example, in the genus Thiocys- 

 tis among the Beggiatoaceae, belong to this class of chromo- 

 genic organisms. Pigmented protoplasm of this character is 

 also noted in those species of bacteria (Bact. chlorinum) (Bacil- 

 lus virens, etc.), which are closely related to the Cyanophyta. 

 (blue-green algae), and in which coloring matter similar to 

 chlorophyll is found. 



There is still another class of chromogenic bacteria in which, 

 by the aid of the microscope, the pigment granules can be seen 

 to be definitely contained within the cell wall. Chromogenic 

 bacteria of this class are called parachromatophorous. Bacillus 

 violaceous is a typical example of a bacterium belonging to 

 this class. 



Pigment production in the majority of bacteria is of practi- 



