FAMILY VII. MICROCOCCACEAE 455 



2. Cells occur in packets. White, jellow, orange and red chromogenesis. Usuall}^ 

 non-motile. 



Genus IV. Sarcina, p. 467. 

 II. Obligate anaerobes occurring singly or in pairs, chains or masses but never in packets; 

 tetrads are rarely formed. 



A. Methane produced from various organic compounds. 



Genus V. Methanococcus, p. 473. 



B. Methane not produced. 



Genus VI. Pepfococcus, p. 474. 



Genus I. Micrococcus Cohn, 1872.*"^ 



(Cohn, Beitrage z. Biol. d. Pflanzen, 1, Heft 2, 1872, 153; 

 Urococcus Miquel, Ann. Microg., 1, 1888, 518.) 



Mi.cro.coc'cus. Gr. adj. micrus small; Gr. noun coccus a grain, berry; M.L. mas.n. Micro- 

 coccus small coccus. 



Cells in irregular masses (never in packets). The group is regarded as Gram-positive al- 

 though some species lose their power to retain the Gram stain so quickly that they are fre- 

 quently reported as Gram-negative. Some species are motile or show motile varieties. 

 Growth on agar usually abundant; some species form no pigment but others form yellow, 

 orange or red pigment. Catalase-positive so far as known. Glucose broth slightly acid, lac- 

 tose broth generally neutral. Gelatin frequently liquefied, but never rapidlj'. Saprophytic, 

 facultatively parasitic or parasitic. Never truly pathogenic. 



The type species \s Micrococcus luteus (Schroeter) Cohn. 



Key to the species of genus Micrococcus. 



I. May or may not reduce nitrates to nitrites. No free nitrogen or nitrous oxide gas pro- 

 duced from nitrates. 



A. No pink or red pigment produced on agar media in young cultures. 

 1. Nitrites not produced from nitrates. 



a. Utilize NH4H2PO4 as a sole source of nitrogen. { 



b. Yellow pigment produced on agar media. Not acido-proteolytic. 

 1. Micrococcus luteus. 



* Revised by Prof. G. J. Hucker and Prof. Robert S. Breed, New York State Experiment 

 Station, Cornell University, Geneva, New York, April, 1954. 



t In revising the material covering the micrococci for the 7th edition of the Manual, it 

 has become evident that there is a very real difference between the fundamental physiolo- 

 gies of such free-living species as those found in soil, sea water and brines, and those that 

 are familiar as pus-forming, enterotoxin-producing staphylococci. The former are able to 

 satisfy their needs for nitrogen and carbon from such simple compounds as ammonium phos- 

 phate and glucose, ammonium tartrate or asparagine and glucose. On the other hand, the 

 staphylococci require more complex nitrogenous compounds in order to grow. It is believed 

 that when suitable investigations can be completed, it will prove desirable to separate the 

 mass-forming cocci into the two genera Micrococcus Cohn, 1872, and Staphylococcus Rosen- 

 bach, 1884. In the present edition both of these genera are recognized. However, only two 

 species have been placed in the genus Staphylococcus; further investigations may show that 

 other parasitic or pathogenic species should be included therein. 



J 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 and 0.02 per cent magnesium sulfate. Add brom-cresol-purple as an indicator 

 (Hucker, N. Y. State Exp. Sta. Tech. Bui. 100, 1924, 25; also Tech. Bui. 101, 1924, 36-40). 



