FAMILY I. NITROBACTERACEAE 



73 



ag'il.is. L. adj. agilis agile, quick. 



Rods, 0.5 by 0.8 to 0.9 micron, occurring 

 singly, sometimes in pairs or larger aggre- 

 gates. Rapidly motile with a long, thin, 

 polar flagellum often 7 to 10 times as long as 

 the rod. (Non-motile culture obtained by 

 Kingma Boltjes, Arch. f. Mikrobiol., 6, 

 1935, 79.) Gram-negative. 



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 transparent 

 colonies. Oxidation usually complete in 10 

 to 14 days. 



Inorganic liquid medium containing ni- 

 trite: Produces uniformly dispersed growth. 



Optimum pH, between 7.6 and 8.6. Limits 

 of growth, 6.6 to 10.0. 



Temperature relations: Optimum for 

 growth, between 25° and 30° C. Optimum 

 for oxidation, 28° C. No oxidation at 37° C. 

 Thermal death point, 60° C. for five min- 

 utes. 



Strictly autotrophic. 



Aerobic. 



Source: Isolated from greenhouse soils 

 and from sewage effluents in Madison, 

 Wisconsin. 



Habitat: Presumably widely distributed 

 in soil. 



Genus VII. Nitrocystis H. Winogradsky , 1935. 

 (Trans. Third Intern. Cong. Soil Sci., Oxford, 1, 1935, 139.) 



Ni.tro.cyst'is. Gr. noun nitrum nitre, M.L. nitrate; Gr. noun cyslis bladder, cj'st; M.L. 

 fem.n. Nitrocystis nitrate cyst. 



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

 aggregates. Oxidize nitrites to nitrates. 



It has been suggested that these organisms were really myxobacters. See note under 

 Nitrosocystis for references. 



The type species is Nitrocystis sarcinoides H. Winogradsky. 



1. Nitrocystis sarcinoides H. Wino- 

 gradsky, 1937. {Nitrocystis B. A., H. Wino- 

 gradsky, Compt. rend. Acad. Sci., Paris, 

 200, 1935, 1888; also see Ann. Inst. Past., 

 58, 1937, 336.) 



sar.cin.o.i'des. L. sarcina a packet; Gr. 

 idus form, shape; M.L. adj. sarcinoides re- 

 sembling Sarcina, a genus of bacteria. 



Small rods 0.5 by 1.0 micron. Cells ellip- 

 soidal or wedge-shaped and grouped in sar- 

 cina-like packets. 



Colonies on silica gel : On the surface of 

 gel coated with kaolin the colonies appear 

 as small, raised, amber warts. The colonies 

 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. 



Babitat: Unknown. 



2. Nitrocystis micropunctata (H. 



Winogradsky, 1935) H. Winogradsky, 1937. 

 (Nitrocystis "III", H. Winogradsky, Trans. 

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

 1935, 139; Nitrogloea micropiinctata H. 

 Winogradsky, Compt. rend. Acad. Sci., 

 Paris, 200, 1935, 1888; H. Winogradsky, 

 Ann. Inst. Past., 58, 1937, 326.) 



mi.cro.punc.ta'ta. Gr. micrus small; L. 

 punctatus spotted; M.L. adj. micropunctatus 

 full of small spots. 



Cells are ellipsoidal rods, about 0.5 mi- 

 cron in diameter, which stain poorly except 

 at the ends. Encased in a viscous slime. 



Colonies on silica gel: Like those of A^. 

 sarcinoides except that they are clearer and 

 have a more plastic consistency. 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. 



