CHAPTER XII. 

 THE GENUS RHODOCOCCUS. 



The cocci which produce a reddish or pinkish pigment 

 have been classed by ^systematic bacteriologists in the 

 genera Micrococcus and Sarcina, according to the form 

 of cell grouping observed. They form the ninth group of 

 Chester's Micrococcus (aerobic and facultative anaerobic, 

 — distinctly chromogenic, — pigment reddish, pinkish, 

 flesh-colored) and the fifth group of his Sarcina (red 

 growth on gelatin and agar). In Migula's scheme the 

 fourth main group of the micrococci and sarcinae culti- 

 vated on gelatin includes, in each case, the red forms. 



Quantitative study of the biological properties of the 

 red chromogenic cocci in our own series furnished strong 

 evidence of their relation to each other, and of their marked 

 difference from all other members of the family. We 

 found only twenty-five of these organisms; but their group 

 characters were so definite and constant that even this 

 small number seemed to warrant the creation of the genus 

 Rhodococcus. 



First, all our red cocci, but one, were from saprophytic 

 sources, eight from water, seven from earth, and nine 

 from air. Among the yellow micrococci and the sarcinae 

 about a quarter of the cultures were of parasitic origin. 



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