236 MANUAL OF DETERMINATIVE BACTERIOLOGY 



pigment but others form yellow or less commonly orange, or red pigment. Glucose 

 broth slightly acid, lactose broth generally neutral. Gelatin frequently liquefied, 

 but not rapidly. Facultative parasites and saprophytes. 

 The type species is Micrococcus luieus (Schroeter) Cohn. 



Key to the species of genus Micrococcus. 

 1. Aerobic to facultative anaerobic species. 

 I. No pink or red pigment on agar media. 



A. Nitrites not produced from nitrates. 



1. Utilize NH4H2PO4 as sole source of nitrogen.* 



--. - a. Yellow pigment on agar media. Not acido-proteolytic, 



1. Micrococcus liiteus. 

 aa. No pigment produced. Not acido-proteolytic. 



b. Utilizes urea as a sole source of nitrogen.** 



2. Micrococcus ureae. 

 bb. Does not utilize urea. 



3. Micrococcus freudenreichii. 

 aaa. Acido-proteolytic in litmus milk. 



8. Micrococcus caseolyticus. 



2. Do not utilize NH4H2PO4 as sole source of nitrogen. 



a. Yellow pigment produced. 



4. Micrococcus flavus. 

 aa. No pigment produced. 



5. Micrococcus candidus. 



B. Nitrites produced from nitrates. 



1. Utilize NH4H2PO4 as sole source of nitrogen. 



a. Yellow pigment on agar media. Not acido-proteolytic. 

 b. Gelatin liquefied. 



6. Micrococcus conglomeratus . 

 bb. Gelatin not liquefied. 



7. Micrococcus varians. 



aa. Usually not chromogenic. Actively acido-proteolytic inlitmus milk. 



S. Micrococcus caseolyticus. 



2. Do not utilize NH4H2PO4 as sole source of nitrogen. 



a. Gelatin liquefied. Ferment mannitol. 

 b. Abundant orange growth on agar media. 



9a. Micrococcus pyogenes var. aureus. 

 bb. Abundant white growth on agar media. 



9b. Micrococcus pyogenes var. albus. 

 bbb. Yellow growth on agar media. 



10. Micrococcus citreus. 

 aa. Gelatin not liquefied or very slowly liquefied. 



b. Abundant orange to white growth on agar media. Ferments 

 mannitol. 



11. Micrococcus aurantiacus. 



bb. Scant white translucent growth on agar media. Does not 

 ferment mannitol. 



12. Micrococcus epidermidis. 



* That is, will grow and produce acid (sometimes slowly) on slants containing 

 1.5 per cent washed agar, 0.1 per cent ammonium phosphate, 1.0 per cent glucose, 

 0.02 per cent potassium chloride, 0.02 per cent magnesium sulfate. Add brom-cresol- 

 purple as an indicator (Hucker, N. Y. State E.xper. Sta., Tech. Bui. 100, 1924, 25; 

 Tech. Bui. 101, 1924, 36-40) ; Manual Pure Culture Study of Bacteria. Soc. Amer. 

 Bact., Geneva, N. Y., Leaflet II, 9th ed., 1944, 14.) 



