FAMILY I. NITROBACTERACEAE 



1. Nitrosomonas europaea Winograd- 

 sky, 1892. (Arch. Sci. biol., St. Petersburg, 

 1, 1892, 127.) 



eu.ro. pae'a. Gr. adj. europaeus of Europe, 

 European. 



Rods, 0.9 to 1.0 by 1.1 to 1.8 microns, oc- 

 curring singly, rarely in chains of three to 

 four. Possess a single polar flagellum 3 to 4 

 times the length of the rods, or rarely one 

 at either end. 



Grow readily in aqueous media without or- 

 ganic matter and containing ammonium 

 sulfate, potassium phosphate and mag- 

 nesium carbonate. The cells accumulate in 

 soft masses around the particles of mag- 

 nesium carbonate at the bottom of the flask. 

 The liquid is occasionally turbid through 

 development of motile swarm cells or 

 monads. 



Small, compact, sharply defined colonies 

 brownish in color on silica gel. 



Aerobic. 



Strictly autotrophic. 



Source: Soils of Zurich, Switzerland; of 

 Gennevilliers, France; and Kazan, Russia. 



Habitat: Presumably widely distributed 

 in soil. 



2. Nitrosomonas monocella Nelson, 

 1931. (Zent. f. Bakt., II Abt., 83, 1931, 287.) 



mon.o.cel'la. Gr. monus single; L. cella 

 oom, cell; M.L. adj. monocellus one-celled. 



Ovoid rods, 0.6 to 0.9 micron, often oc- 

 curring in pairs. Young cells nearly spheri- 

 cal. Motile by means of a single polar 

 flagellum 3 to 5 times as long as the rod. 

 Gram-positive (Nelson). Found negative by 

 H. J. Conn (personal communication). 



No growth in nutrient broth, nutrient 

 agar, nutrient or plain gelatin, plain or lit- 

 mus milk, glucose or plain yeast water, or on 

 potato. 



Silica gel or agar plates of inorganic 

 medium: No typical colonies, but yellowish 

 brown masses of growth around particles of 

 CaCOs in the medium. 



Inorganic liquid medium containing 

 ammonium salts: Uniform development 

 throughout the liquid as well as in the 

 carbonate sediment. 



Even low concentrations of organic mat- 

 ter retard or completely inhibit the initia- 

 tion of growth. Plant extracts are toxic. 



Free CO 2 and O2 necessary for growth. 



Optimum pH, 8.0 to 9.0. Poor growth 

 below pH 7.0. Some growth above pH 9.0. 



Optimum temperature for growth and oxi- 

 dation, 28° C. 



Aerobic . 



Strictly autotrophic. 



Source: Isolated from field soil. 



Habitat: Presumably widely distributed 

 in soil. 



Genus II. Nitrosococcus Winogradshj, 1892. 

 (Arch. Sci. biol., St. Petersburg, 1, 1892, 127.) 

 Ni.tro.so.coc'cus. M.L. nitrosus nitrous; Gr. coccus grain, berry; M.L. mas.n. Nitroso- 

 coccus nitrous sphere. 



Cells large spheres, non-motile, not producing zoogloeae. Oxidize ammonia to nitrite. 

 The type species is Nitrosococcus nitrosus (Migula) Buchanan. 



1. Nitrosococcus nitrosus (Migula, 

 1900) Buchanan, 1925. {Nitrosococcus Wino- 

 gradsky, Ann. Inst. Past., 5, 1891, 577; 

 Arch. Sci. biol., St. Petersburg, 1, 1892, 127; 

 Micrococcus nitrosus Migula. Sj^st. d. Bakt., 

 2, 1900, 194; Buchanan, Gen. Syst. Bact., 

 1925, 402.) 



ni.tro'sus. M.L. adj. nitrosus nitrous. 



Large spheres, 1.5 to 1.7 microns in size, 

 with thick cell membranes. Motility could 

 not be demonstrated. Stain readily with 



aniline dyes. Zoogloea formation not ob- 

 served. Gram-positive (Omelianski, Cent. f. 

 Bakt., II Abt., 19, 1907, 263). 



Liquid medium: Turbid. 



Silica gel: Both dark and light colonies. 

 Surface colonies look like small drops of a 

 turbid yellowish liquid. 



Aerobic. 



Optimum temperature, lietween 20° and 

 25° C. 



Source: Isolated from .soil from (^uito. 



