FAMILY NITROBACTERIACEAE 



75 



No growth in nutrient broth, nutrient 

 agar, nutrient or plain gelatin, litmus or 

 plain milk, glucose or plain yeast water, 

 or on potato. 



Nitrite agar : After two weeks, produces 

 semi-spherical, minute, nearly transpar- 

 ent colonies. Oxidation usually com- 

 plete in 10 to 14 days. 



Inorganic liquid medium containing 

 nitrite : Produces uniformly dispersed 

 growth. 



Optimum pH 7.6 to 8.6. Limits of 

 growth 6.6 to 10.0. 



Temperature relations: Optimum for 

 growth 25° to 30°C. Optimum for oxida- 

 tion 28°C. No oxidation at 37°C. Ther- 

 mal death point 60°C. for five minutes. 



Strictly autotrophic. 



Aerobic. 



Source : Isolated from greenhouse soils 

 and from sewage effluents in Madison, 

 Wisconsin. 



Habitat: Presumably widely distrib- 

 uted in soil. 



Genus VII. Nitrocystis H. Winogradsky. 



(Trans. Third Intern. Cong. Soil Sci., O.xford, i, 1935, 139 ; Nitrogloea H. Winogradsky, 

 Comp. rend. Acad. Sci., Paris, 200, 1935, 1888.) 



Cells ellipsoidal or rod-shaped. Embedded in slime and united into compact zoo- 

 gloeal aggregates. Oxidize nitrite to nitrate. From Latin, nitrum, soda; M.L. 

 nitre; and Greek, kystis, bladder; M.L. nitric cyst. 



The type species is Nitrocystis sarcinoides. 



1. Nitrocystis sarcinoides H. Wino- 

 gradsky. {Nitrocystis B. A., Winograd- 

 sky, H., Compt. rend. Acad. Sci., Paris, 

 200, 1935, 1888; Nitrocystis "/" and 

 "//", Winogradsky, H., Trans. Third 

 Intern. Cong. Soil Sci., Oxford, 1, 1935, 

 139; Ann. Inst. Pasteur, 58, 1937, 336.) 

 From Latin, sarcina, a packet; M.L. 

 Sarcina, a genus; Greek, eidos, form; 

 M.L. Sarcina-like. 



Rods: Small rods 0.5 by 1.0 micron. 

 Cells ellipsoidal or wedge-shaped and 

 grouped in sarcina-like packets. 



Colonies on silica gel : On the surface of 

 gel coated with kaolin the colonies appear 

 as small raised amber warts. The colon- 

 ies grow up to 5 mm. in diameter. The 

 colonies are viscous and sticky when 

 young and they become brown with age, 

 shrink, and look like scales and become 

 hard like grains of sand. Each colony is 

 enveloped in several layers of a thick 

 slime which holds the cells together so 

 that the entire colony can be removed 

 with a transfer needle. 



Aerobic. 



Source: Activated sludge. 



Habitat: Unknown. 



2. Nitrocystis micropunctata H. Wino- 

 gradsky. {Nitrocystis "III", Wino- 

 gradsky, H., Trans. Third Intern. Cong. 

 Soil Sci., Oxford, 1, 1935, 139; Nitrogloea 

 micropunctata Winogradsky, H., Compt. 

 rend. Acad. Sci., Paris, 200, 1935, 1888; 

 Ann. Inst. Pasteur, 58, 1937, 326.) From 

 Greek, mikros, small, little; and Latin, 

 punctatus, spotted; M.L. with small 

 spots. 



Cells are ellipsoidal rods about 0.5 

 micron in diameter which stain poorly 

 except at the ends. Encased in a viscous 

 slime. 



Colonies on silica gel : Like N, sar- 

 cinoides except that the colonies are more 

 clear and they have a more plastic con- 

 sistency. The cells are not held together 

 by the slime in the colony as with N. 

 sarcinoides. The capsule is more readily 

 differentiated in old colonies. 



Aerobic. 



Source: Activated sludge. 



Habitat: Unknown. 



Appendix: The following have been 

 placed in the Tribe Nitrobacterieae, some- 

 times incorrectly so : 



Bactoderma alba Winogradsky. (Aim. 



