Nitrosospira

Nitrosospira is a genus of ammonia-oxidizing bacteria in the family Nitrosomonadaceae, within the class Betaproteobacteria. Members are chemolithoautotrophs that derive energy by oxidizing ammonia to nitrite and fix carbon dioxide for growth. They contribute to the biological nitrification of nitrogenous compounds in a range of environments, including soil, freshwater, and engineered systems such as wastewater treatment plants.

Taxonomy and morphology commonly place Nitrosospira in the order Nitrosomonadales. The cells are typically Gram-negative, rod-shaped, and often motile. As autotrophs, they rely on inorganic carbon sources and oxygen, and their metabolism is centered on ammonia oxidation, initiated by ammonia monooxygenase and followed by hydroxylamine oxidation to nitrite.

Ecology and occurrence vary with species and environment. Nitrosospira species are found in soils, sediments, and aquatic habitats, frequently contributing to ammonia turnover at low to moderate substrate concentrations. They are often studied alongside other ammonia-oxidizing bacteria to understand nitrification dynamics and nitrogen cycling in ecosystems.

Notable species include Nitrosospira multiformis, Nitrosospira tenuis, and Nitrosospira briensis. Genomic and molecular studies frequently target the amoA gene, which encodes a key component of the ammonia-oxidizing enzyme complex, to assess diversity and activity in environmental samples. Nitrosospira remains an important genus for understanding nitrification, wastewater processes, and microbial ecology of nitrogen cycling.