Ecuador; Campinas, Brazil; and Melbourne, Australia.
Habitat: Presumably widely distributed in soil.
Genus III. Nitrosospira Winogradsky, 1931.
(S. Winogradsky, Compt. rend. Acad. Sci., Paris, 192, 1931, 1004; S. Winogradsky and H. Winogradsky, Ann. Inst. Past., 50, 1933, 394 and 406.)
Ni.tro.so.spi′ra. M.L. nitrosus nitrous; Gr. spira a coil, spiral; M.L. fem. n. Nitrosospira nitrous spiral.
Cells spiral-shaped. Oxidize ammonia to nitrite very slowly.
The type species is Nitrosospira briensis S. Winogradsky and H. Winogradsky.
1. Nitrosospira briensis S. Winogradsky and H. Winogradsky, 1933. (Ann. Inst. Pasteur, 50, 1933, 407.)
bri.en′sis. French Brie, place name; M.L. adj. briensis of Brie.
Spirals wound tightly to form very small cylinders as long as 15 to 20 microns. Short spirals have the appearance of short rods and ellipsoidal cells. Small pseudo-cocci observed in old cultures.
Colonies on silica gel: Small, occasionally containing cyst-like aggregates of cells. The cysts are more poorly developed than in Nitrosocystis.
Aerobic.
Optimum pH, between 7.0 and 7.2.
_Uncultivated pasture soil of Brie, France.
Habitat: Presumably widely distributed in soil.
2. Nitrosospira antarctica S. Winogradsky and H. Winogradsky, 1933. (Ann. Inst. Past., 50, 1933, 407.)
ant.arc′tic.a. Gr. anti opposite; Gr. arctus a bear; Gr. adj. antarcticus opposite the bear, antarctic.
Cells and colonies similar to those of N. briensis except that the cells are generally wound together to form more compact spirals.
Aerobic.
Optimum pH, between 7.0 and 7.2.
Source: Soil from the Antarctic.
Habitat: Presumably widely distributed in soil.
Genus IV. Nitrosocystis Winogradsky, 1931.
(S. Winogradsky, Compt. rend. Acad. Sci., Paris, 192, 1931, 1003; also see S. Winogradsky and H. Winogradsky, Ann. Inst. Past., 50, 1933, 394 and 399.)
Ni.tro.so.cyst′is. M.L. adj. nitrosus nitrous; Gr. noun cystis bladder, cyst; M.L. fem. n. Nitrosocystis nitrous cyst.
Cells ellipsoidal or elongated, uniting in compact, rounded aggregates surrounded by a common membrane to form cysts. The cysts disintegrate to free the cells, particularly when transferred to fresh media. Within the cyst the cells are embedded in slime. Ammonia is oxidized to nitrite at a rate intermediate between that of Nitrosomonas and that of Nitrosospira.
Winogradsky and Winogradsky (ibid., 393) differentiated between Nitrosomonas and Nitrosocystis in that the former produced soft (or clear) colonies and the latter produced hard (or dark) colonies on silica gel. However, Kingma Boltjes (Arch. Mikrobiol., 6, 1935, 79) was able to obtain both hard and soft colonies in cultures of Nitrosomonas derived from single-cell isolates. Meiklejohn (Nature, 168, 1951, 561; also see Jour. Soil Sci., 4, 1953, 62), furthermore, states that the appearance of hard or soft colonies is dependent upon the density of the silica gel and upon whether the colonies are in the gel or on the surface; consequently she regards Nitrosocystis as probably identical with Nitrosomonas. Some observers (Imšenecki, Nature, 157, 1946, 877; and Grace, Nature, 168, 1951, 117; also see Riassunti d. Comunicazione, VI Cong. Internaz. d. Microbiol., Roma, 1, 1953, 53) have
