FAMILY NITROBACTERIACEAE 



71 



polar flagellum 3 to 5 times as long as the 

 rod. Gram-positive (Nelson). Found 

 negative by H. J. Conn (personal com- 

 munication) . 



No growth in nutrient broth, nutrient 

 agar, nutrient or plain gelatin, plain or 

 litmus milk, glucose or plain yeast 

 water, or on potato. 



Silica gel or agar plates of inorganic 

 medium: No typical colonies, but yel- 

 lowish 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 

 matter retard or completely inhibit the 

 initiation of growth. Plant extracts are 

 toxic. 



Free CO2 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 

 oxidation 28°C. 



Aerobic. 



Strictly autotrophic. 



Source: Isolated from field soil. 



Habitat : Presumably widely distrib- 

 uted in soil. 



S. Winogradsky and H. Winogradsky 

 (Ann. Inst. Pasteur, 50, 1933, 394) have 

 described 5 cultures of Nitrosomonas 

 which were obtained from soils of France. 

 An additional culture has been described 

 by H. Winogradsky (Ann. Inst. Pasteur, 

 58, 1937, 394) from activated sludge. 



Genus II. Nitrosococcus Winogradsky. 



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



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

 From Latin, nitrosus, full of soda; and Greek kokkos, grain; M.L. nitrous coccus. 

 The type species is Nitrosococcus nitrosus (Migula) Bergey et al. 



1. Nitrosococcus nitrosus (Migula) 

 Bergey et al. {Nitrosococcus Winograd- 

 sky, Ann. Inst. Pasteur, 6, 1891, 577; 

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

 127; Micrococcus nitrosus Migula, Syst. 

 d. Bakt., ^, 1900, 194 ; Nitrosococcus ameri- 

 canus Buchanan, Jour. Bact., 3, 1918, 

 180; Manual, 2nd ed., 1925, 35.) From 

 Latin, nitrous, full of soda; M.L. nitrous. 



Large spheres, 1.5 to 1.7 microns in 

 size, with thick cell membrane. Motil- 

 ity could not be demonstrated. Stains 

 readily with aniline dyes. Observed 

 no zoogloea formation. Gram-positive 



(Omelianski, Cent. f. Bakt., II Abt., 19, 

 1907, 263). 



Liquid medium: Turbidity. 



Silica gel : Both dark and light colonies. 

 Surface colonies look like small drops of a 

 turbid yellowish liquid. 



Aerobic. 



Optimum temperature 20° to 25°C. 



Source : Isolated from soil from Quito, 

 Ecuador; Companias, Brazil; Melbourne, 

 Australia . 



Habitat : Presumably widely distrib- 

 uted in soil. 



Genus III. Nitrosospira Winogradsky. 



(Compt. rend. Acad. Sci., Paris, 192, 1931, 1004; Ann. Inst. Pasteur, 50, 1933, 406.) 



Cells spiral-shaped. Oxidize ammonia to nitrite very slowly. From Latin, 

 nitrosus, full of soda; and spira, coil, spiral; M.L. nitrous spiral. 

 The type species is Nitrosospira briensis Winogradsky. 



