Nitrosomonas
Encyclopedia
Nitrosomonas is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 comprising rod shaped chemoautotrophic bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

.

This rare bacteria oxidizes ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 into nitrite
Nitrite
The nitrite ion has the chemical formula NO2−. The anion is symmetric with equal N-O bond lengths and a O-N-O bond angle of ca. 120°. On protonation the unstable weak acid nitrous acid is produced. Nitrite can be oxidised or reduced, with product somewhat dependent on the oxidizing/reducing agent...

 as a metabolic process. Nitrosomonas are useful in treatment of industrial and sewage waste and in the process of bioremediation
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...

. They are important in the nitrogen cycle
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...

 by increasing the availability of nitrogen to plants while limiting carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 fixation. The genus is found in soil, sewage, freshwater, and on building surfaces, especially in polluted areas that contains high levels of nitrogen compounds.

Nitrosomonas prefers an optimum pH of 6.0-9.0 and a temperature range of 20 to 30°C. Most species are motile with a flagellum located in the polar regions.

The bacteria has power generating membranes, which form long, thin tubes inside the cell. These use electrons from the oxidation of ammonia to produce energy. It obtains the carbon it requires from the atmosphere via carbon fixation
Carbon fixation
In biology, carbon fixation is the reduction of carbon dioxide to organic compounds by living organisms. The obvious example is photosynthesis. Carbon fixation requires both a source of energy such as sunlight, and an electron donor such as water. All life depends on fixed carbon. Organisms that...

, which converts carbon in a gaseous form into carbon bound in organic molecules.

Unlike plants, which fix carbon into sugar through energy gained through the process of photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

, Nitrosomonas use energy gained through the oxidation of ammonia to fix gaseous carbon dioxide into organic molecules. Nitrosomonas must consume large amounts of ammonia before cell division can occur, and the process of cell division may take up to several days. This microbe is photophobic
Photophobia
Photophobia is a symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical photosensitivity of the eyes, though the term...

, and will cover itself in slime or form clumps with other microbes to avoid light.

The species Nitrosomonas europaea has been identified as also being able to degrade a variety of halogenated compounds including trichloroethylene
Trichloroethylene
The chemical compound trichloroethylene is a chlorinated hydrocarbon commonly used as an industrial solvent. It is a clear non-flammable liquid with a sweet smell. It should not be confused with the similar 1,1,1-trichloroethane, which is commonly known as chlorothene.The IUPAC name is...

, benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

, and vinyl chloride
Vinyl chloride
Vinyl chloride is the organochloride with the formula H2C:CHCl. It is also called vinyl chloride monomer, VCM or chloroethene. This colorless compound is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride . At ambient pressure and temperature, vinyl chloride...

. Some Nitrosomonas species possess the enzyme, urease, which catalyzes the conversion of the urea molecule to two ammonia molecules and one carbon dioxide molecule. Nitrosomonas europaea, as well as populations of soil-dwelling ammonia-oxidizing bacteria, have been shown to assimilate the carbon dioxide released by the reaction to make biomass via the Calvin Cycle
Calvin cycle
The Calvin cycle or Calvin–Benson-Bassham cycle or reductive pentose phosphate cycle or C3 cycle or CBB cycle is a series of biochemical redox reactions that take place in the stroma of chloroplasts in photosynthetic organisms...

, and harvest energy by oxidizing ammonia (the other product of urease) to nitrite. This feature may explain enhanced growth of AOB in the presence of urea in acidic environments.

Some sources regard Nitrobacteraceae
Nitrobacteraceae
Nitrobacteraceae is a family of Alphaproteobacteria. They are gram-negative and aerobic.The bacteria of this family derive their energy from oxidizing ammonia to nitrite, or by oxidizing nitrite to nitrate.They are commonly found in freshwater and soil....

to be the family of the genus Nicosomonas.
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