Nitrospira

Nitrospira (from Latin: nitro, meaning "nitrate" and Greek: spira, meaning "spiral") is a genus of bacteria within the monophyletic clade of the Nitrospirota phylum. The first member of this genus was described 1986 by Watson et al., isolated from the Gulf of Maine. The bacterium was named Nitrospira marina. Populations were initially thought to be limited to marine ecosystems, but it was later discovered to be well-suited for numerous habitats, including activated sludge of wastewater treatment systems, natural biological marine settings (such as the Seine River in France and beaches in Cape Cod in the United States), water circulation biofilters in aquarium tanks, terrestrial systems, fresh and salt water ecosystems, agricultural lands and hot springs. Nitrospira is a ubiquitous bacterium that plays a role in the nitrogen cycle by performing nitrite oxidation in the second step of nitrification. Nitrospira live in a wide array of environments including but not limited to, drinking water systems, waste treatment plants, rice paddies, forest soils, geothermal springs, and sponge tissue. Despite being abundant in many natural and engineered ecosystems Nitrospira are difficult to culture, so most knowledge of them is from molecular and genomic data. However, due to their difficulty to be cultivated in laboratory settings, the entire genome was only sequenced in one species, Nitrospira defluvii. In addition, Nitrospira bacteria's 16S rRNA sequences are too dissimilar to use for PCR primers, thus some members go unnoticed. In addition, members of Nitrospira with the capabilities to perform complete nitrification (comammox bacteria) has also been discovered and cultivated.

==Morphology== For the following description, Nitrospira moscoviensis will be representative of the Nitrospira genus. Nitrospira is a Gram-negative nitrite-oxidizing organism with a helical to vibroid morphology (0.9–2.2 × 0.2–0.4 micrometres in size). They are non-planktonic organisms that reside as clumps, known as aggregates, in biofilms. Visualization using transmission electron microscopy (TEM) confirms star-like protrusions on the outer membrane (6–8 nm thick). The periplasmic space is exceptionally wide (34–41 nm thick), which provides space to accommodate electron-rich molecules. Electron-deprived structures are located in the cytosol and are believed to be glycogen storage vesicles; polyhydroxybutyrate and polyphosphate granules are also identified in the cytoplasm. DNA analysis determined 56.9 +/- 0.4 mol% of the DNA to be guanine and cytosine base pairs.