B 169

Hans-Peter Koops and Andreas Pommerening-ROser

Ni.tro.so.coc'cus. M.L. adj. nitrosus nitrous; coccus a grain, berry; M.L. masc. n. Nitrosococcus nitrous sphere.

Cells are spherical to ellipsoidal (Fig. BXII.y.10A). Typical Gramnegative cell wall, but some strains have additional layers composed of repeating subunits arranged in a molecular array (Watson and Remsen, 1969, 1970). Extensive intracytoplasmic membrane systems arranged centrally in the protoplasm (Fig. BXII.y.10B). Carboxysomes not observed. Obligate salt requirement. Urea can be used as ammonia source by one of the two described species. Motile cells possess a tuft of flagella or a single flagellum. Species are distributed in oceans and in salt lakes.

Type species: Nitrosococcus nitrosus (Migula 1900) Buchanan 1925, 402 (Nom. Cons. Opin. 23 Jud. Comm. 1958b, 169) (Micrococcus nitrosus Migula 1900, 194.)

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