User:Marty ariel97/sandbox

Morphology
Three basic morphological types of Nitrosomonas were founded, which are: short rods Nitrosomonas, rods Nitrosomonas and Nitrosomonas with pointed ends. Cells of Nitrosomonas species have a polyhedral inclusion bodies which are present in both growing and resting cells; these bodies are located in the nucleoplasm. Nitrosomonas species cells have different criteria of size and shape.

Nitrosomonas europaea shows short rods with pointed ends cells, which size is (0.8-1.1 x 1.0- 1.7) µm; motility has not been observed. Their preferred habitats are sewage disposal plants, eutrophic freshwater and fertilized soils.

Nitrosomonas eutropha presents rod to pear shaped cells with one or both ends pointed, with a size of (1.0-1.3 x 1.6- 2.3) µm. They have been shown motility and their favorite habitats are sewage disposal plants or eutrophic environments.

Nitrosomonas halophila cells have a coccoid shape and a size of (1.1-1.5 x 1.5- 2.2) µm. Motility is possible because of a tuft of flagella. They are usually found in brackish water.

Nitrosomonas communis shows large rods with rounded ends cells which size is (1.0-1.4 x 1.7- 2.2) µm. Motility has not been observed here. They usually live in moderate eutrophic pH neutral soils and freshwater.

Nitrosomonas nitrosa, N. oligotropha and N. ureae cells are spheres or rods with rounded ends. Motility has not been observed in them as well. While N. nitrosa prefer eutrophic freshwater, marine environment, or wastewater treatment plants, N. oligotropha and N. ureae prefer oligotrophic freshwater and natural soils.

Nitrosomonas marina present slender rods with rounded ends cells with a size of (0.7-0.9 x 1.7- 2.2) µm. They are usually found in marine environment.

Nitrosomonas aestuarii and Nitrosomonas cryotolerans present rod shaped cells and they both can be found in marine environment as well as N. Marina.

Genetics [edit]
Among the various species of Nitrosomonas that are known today, the complete genome of N. ureae strain Nm10, N. europaea, N.sp. Is79 has been sequenced.

All these species are characterized by the presence of the genes for the ammonia oxidation. The first enzyme involved in the ammonia oxidation is ammonia monooxygenase (AMO), which is encoded by the amoCAB operon. The AMO enzyme catalyzes the oxidation from (ammonia) to  (hydroxylamine). The amoCAB operon contains three different gene: amoA, amoB and amoC. While N. europaea presents two copy of the genes, N. ''sp. Is79'' and N. ureae strain Nm10 have three copy of these gene.

The second enzyme involved in the ammonia oxidation is hydroxylamine oxidoreductase (HAO) encoded by the hao operon. This enzyme catalyzes the oxidation from   to. The hao operon contains different genes such as the haoA that encodes for the functional cytochrome c subunit; the cycA that endodes for cytochrome c554 and the gene cycB that encodes for quinone reductase. These genes are present in different copies in various species; for instance, in ''Nitrosomonas sp. Is79'' there are only three copy, while in N. ureae there are four.

Nitrosomonas uses the Calvin-Benson cycle as a pathway for the Carbon fixation. for this reason all the species present an operon that encodes for the RuBisCO enzyme. A peculiarity is found in N. sp Is79 in which the two copy of the operon encode for two different forms of the RuBisCO: the IA form and the IC form, where the first one has major affinity with the Carbon dioxide. Other species present different copies of this operon that encodes only for the IA form.

Important was the discovery of genes that encodes for enzymes involved in the denetrification. the first gene involved in this process is nirK that encodes for a Nitrite reductase with Copper. this enzyme catalyzes the reduction form (Nitrite) to (Nitric oxide). While in N. europaea, N. eutropha and N. cryotolerans nirK is included in a multigenetic cluster ; in ''Nitrosomonas sp. Is79 and N. sp. AL212'' it is present as a single gene. An high expression of the nirK gene was found in N.ureae and this has been explained with the hypothesis that the NirK enzyme is also involved in the oxidation of  in this species. The second genes involved in the denitrification are norCBQD that encodes for a nitric-oxide reductase that catalyzes the reduction from (Nitric oxide) to (NItrous oxide). These genes are present in ''N. sp. AL212, N.cryotolerans and N. communis strain Nm2''. In the Nitrosomonas europaea these genes are included in a cluster. These genes are absent in N. sp. Is79 and N. ureae.

Recently is found the norSY gene that encodes for a nitric-oxide reductase with copper in N. communis strain Nm2 and Nitrosomonas AL212.

Ammonia-oxidation
Nitrosomonas is a genus comprising Gram-negative, rod-shaped, and chemoautotrophic bacteria.

Nitrosomonas are one of the genera included in the ammonia-oxidizing bacteria (AOB). AOB use ammonia as energy source and carbon dioxide as the main source of carbon. The oxidation of ammonia is a rate-limiting step in nitrification and plays a fundamental role in the nitrogen cycle, because it transforms ammonia, which is usually extremely volatile, into less volatile forms of nitrogen.

Nitrosomonas oxidize ammonia into nitrite in a metabolic process, known as nitritation (a step of nitrification). This process occurs with the accompanying  reduction of an oxygen molecule to water (which requires four electrons), and the release of energy. The oxidation of ammonia to hydroxylamine is catalyzed by ammonia monooxygenase (AMO), which is a membrane-bound, multisubstrate enzyme. In this reaction two electrons are required to reduce an oxygen atom to water :

NH3 + O2 + 2 H+ + 2 e– → NH2OH + H2O

Since an ammonia molecule only releases two electrons when oxidized, it has been assumed that the other two necessary electrons come from the oxidation of hydroxylamine to nitrite, which occurs in the periplasm and it is catalyzed by hydroxylamine oxidoreductase (HAO), a periplasm associated enzymes.

NH2OH + H2O → NO2– + 5 H+ + 4 e–

Two of the four electrons released by the reaction, return to the AMO to convert the ammonia in hydroxylamine. 1,65 of the two remaining electrons are available for the assimilation of nutrients and the generation of the proton gradient. They pass through the cytochrom c552 to the cytochrome caa3, then to O2, which is the terminal acceptor; here they are reduced to form water. The remaining 0,35 electrons are used to reduce NAD+ to NADH, to generate the proton gradient.

Nitrite is the major nitrogen oxide produced in the process, but it has been observed that, when low oxygen concentrations are low, nitrous oxide and nitric oxide can also form, as by-products from the oxidation of hydroxylamine to nitrite.

Nitrosomonas are useful in a polluted water and waste treatment technique known as bioremediation. They are important in the nitrogen cycle as they increase the bioavailability of nitrogen to plants whilst limiting carbon fixation. The genus is found in soil, freshwater, and on building surfaces, especially in areas that contains high levels of nitrogen compounds.

Nitrosomonas thrive in a pH range of 6.0–9.0, and a temperature range of 20–30 C. Most species are motile with a flagellum located in the polar region of the bacillus.

The organism 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, which converts gaseous carbon dioxide into carbon bound in 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, and will generate a biofilm matrix, or form clumps with other microbes, to avoid light.

The species Nitrosomonas europaea has been identified as being able to degrade a variety of halogenated compounds including trichloroethylene, benzene, and vinyl chloride. Some Nitrosomonas species possess the enzyme urease, which catalyzes the conversion of the urea into ammonia and carbon dioxide. N. europaea, as well as populations of soil-dwelling ammonia-oxidizing bacteria (AOB), have been shown to assimilate the carbon dioxide released by the reaction to make biomass via the Calvin cycle, 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 to be the family of the genus Nicosomonas.

Ecology
Habitat

Nitrosomonas spp. is generally found in highest numbers in all habitat in which there is abundance of ammonia ( environment with plentiful protein decomposition or in wastewater treatment); since do not like being exposed to light, usually cover in aggragates with other microbes to avoid it. Some species can live and proliferate on monuments’ surface or on stone buildings’ walls, causing frequently erosion.

It is globally distributed in both freshwater and saltwater, emerging especially above all in shallow coastal sediments and under the upwelling zones, such as the Peruvian coast and the Arabian Sea.

Nitrification

Chemolithoautotrophic ammonia-oxidizing bacteria like Nitrosomonas are responsible for the rate-limiting step of nitrification in a wide variety of environments, giving them important key role in the global cycling of nitrogen, especially in the ocean.

In agriculture, nitrification made by Nitrosomonas spp., represents a problem because the oxidized nitrite by ammonia can persist in the soil, leaching, and making it less available for plants.

Nitrification can be slowed down by some inhibitors that are able to slow down the oxidation process of ammonia to nitrites by inhibiting the activity of bacteria of the genus Nitrosomonas and other ammonia-oxidizing bacteria, minimize or prevent the loss of nitrate.

Application

Nitrosomonas is used in activated sludge in aerobic wastewater treatment; the reduction of nitrogen compounds in the water is given by nitrification treatment in order to avoid environmental issues, such as ammonia toxicity and groundwater contamination. Nitrogen, if present in high quantities can cause algal development, leading to eutrophication with degradation of oceans and lakes.

Employing as wastewater treatment biological removal of nitrogen is obtained a lower economic expense and less damage caused to the environment compared to physical-chemical treatments.

Nitrosomonas has a role in biofilter systems, tipically in association and collaboration with other microbs, to consume compounds such as ammonia or CO2and recycle nutrients. These systems are used for various purposes but mainly for the elimination of odors from waste treatment.

Healh/medical benefits

Nitrosomonas europaea is a non-pathogenic bacteria which has been studied in connection with the probiotic therapies, may giving aesthetic benefits in terms of reducing the appearance of wrinkles. The effectiveness of the probiotic products has been studied to explore why Nitrosomonas eutropha which is a highly mobile bactreruim have became extint from the normal flora of our skin. This study is in connection with the idea of having benefits through the repopulation and reintroduction of Nitrosomonas eutropha to the normal flora of human skin.