Nitrosospira

Ni.tro.so.spi' ra . M.L. adj. nitrosus nitrous; Gr. n. spira a coil, spiral; M.L. fem. n. Nitrosospira nitrous spiral. Proteobacteria / Betaproteobacteria / Nitrosomonadales / Nitrosomonadaceae / Nitrosospira Cells are tightly coiled spirals (Figure 1a), 0.3–0.4 µm in width, with 3–20 turns. Occasionally, vibrioid cells occur in cultures. By phase‐microscopy, spherical forms 0.8–1.2 µm in diameter may be observed in cultures. Gram‐negative cell wall. Intracytoplasmic membranes are rare (Figure 1b), but tubular invaginations are observed. Motile strains possess peritrichous flagella . 1–6 flagella are observed, each 3–5 µm in length. Urease‐positive strains, as well as urease‐negative strains, exist in all species. Common in grasslands, heath, forest soils, and mountainous environments. Some strains have been isolated from building stones and from acid soils (pH 4.0–4.5). Occasionally observed in freshwater environments. Using molecular ecological methods, the existence of Nitrosospira ‐like groups in marine environment has repeatedly been indicated (Stephen et al., 1996; Phillips et al., 1999; Bano and Hollibaugh, 2000). However this has not yet been proven via isolation of strains. The mol % G + C of the DNA is : 53.2–55.4. Type species : Nitrosospira briensis Winogradsky and Winogradsky 1933, 407.