FAMILY VII. MICROCOCCACEAE 



473 



monium salts and sub-optimal concentra- 

 tions of other nutrients should be used; also, 

 the reactions of the media should approach 

 the limiting acidity for growth, and the in- 

 cubation temperature should not exceed 

 22° C. 



Motility: After 24 hours, jirimary cul- 



tures on agar, in peptone water and in 

 broth are non-motile whereas those on urea 

 agar are actively motile. 



Source: Isolated from urine and from 

 garden soil. Also found in sea water (Wood, 

 loc. cit.). 



Habitat: Presumably widely distributed. 



Genus V. Methanococcu.s Kluyver and van Niel, 1936, emend. Barker, 1936* 



(Kluyver and van Niel, Zent. f. Bakt., II Abt., 9J^, 1936, 400; Barker, 

 Arch. f. Mikrobiol., 7, 1936, 430.) 



Me.tha.no.coc'cus. Gr. noun methy wine; M.L. noun methanum methane; Gr. noun 

 coccus a berry; M.L. noun coccus a spherical cell; M.L. mas.n. Methanococcus methane 

 coccus. 



Spherical cells, occurring singly, in pairs, or in masses. Motile or non-motile. Gram- 

 variable. Chemo-heterotrophic, fermenting various organic compounds with the production 

 of methane. Anaerobic. Saprophytes. 



The type species is Methanococcus mazei Barker. 



1. Methanococcus niazei Barker, 1936. 

 (Pseudosarcina, Maze, Compt. rend. Soc. 

 Biol., Paris, 78, 1915, 398; Barker, Arch. f. 

 Mikrobiol., 7, 1936, 430.) 



ma'ze.i. M.L. gen .noun mazei of Maze; 

 named for P. Maze, the French bacteriolo- 

 gist who first gave a clearh^ recognizable 

 description of this tj'pe of methane or- 

 ganism. 



Small, spherical cells occurring singh", in 

 large, irregular masses or in regular cysts of 

 various sizes and forms. Non-motile. Stains 

 readily with erythrosine. Gram-variable. 



Grows in a mineral medium containing 

 acetate, fermenting the acetate vigorously. 



Ferments acetate and butyrate with the 

 production of methane and carbon dioxide. 

 Ethanol and butanol not attacked. 



Ammonia nitrogen utilized, but not ni- 

 trate nitrogen. Yeast extract is not bene- 

 ficial. 



Anaerobic. 



Optimum temperature, between 30° and 

 37° C. 



Source: Isolated from garden soil, sewage 

 sludge, black mud containing hydrogen 

 sulfide and from the feces of herbivorous 

 animals. 



Habitat: One of the most active methane- 

 producing organisms found in nature. 



2. Methanococcu.s vannielii Stadtman 

 and Barker, 1951. (Jour. Bact., 62, 1951, 

 269.) 



van.niel'i.i. M.L. gen. noun vannielii of 

 van Niel; named for C. B. van Niel, the 

 American bacteriologist who developed the 

 carbon dioxide reduction theory of methane 

 formation. 



Cocci, often slightly ellipsoidal, which 

 vary from 0.5 to 4.0 microns in diameter 

 and which frequently occur in pairs. Motile. 

 Cells disintegrate on drying. Stain readily 

 with erj^throsine. Gram stain not recorded. 



Agar deep colonies: 0.5 to 1.0 mm in di- 

 ameter, lenticular and light brown with 

 edges regular or slightly lobate. 



Acetate, propionate, butyrate, succinate, 

 glucose, ethanol and methanol are not at- 

 tacked when incorporated in a mineral-bi- 

 carbonate medium of pH 8.0 at a concentra- 

 tion of 0.5 per cent; under similar 

 conditions, formate supports good growth. 



Sodium formate in concentrations of 1.5 

 per cent permits maximum growth; at the 

 2 and 3 per cent levels, growth is slower, 

 and in 5 per cent sodium formate there is no 

 growth. 



Formate, the only organic compound 

 known to support growth, is fermented to 



Prepared by Prof. H. A. Barker, University of California, Berkeley, California, October, 



1955. 



