Nitrososphaera viennensis

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A Microbial Biorealm page on the genus Nitrososphaera viennensis

Classification

Higher order taxa

Archaea; Thaumarchaeota; Nitrososphaerales; Nitrososphaeraceae

Species

Nitrososphaera viennensis

Nitrososphaera viennensis From: ScienceDaily

NCBI: Taxonomy

Description and significance

N. viennensis is a slightly irregular, spherically shaped ammonia oxidizing archaeon with a cell diameter of approximately 0.5-0.8 μm⁽³⁾. It was the first cultivated terrestrial archaeal ammonia oxidizer⁽³⁾.

Etymology: L. adj. nitrosus, "full of natron," (nitrite producer); L. fem. n. sphaera, spherically shaped; L. viennensis, isolated from Vienna ⁽³⁾

Genome structure

The sequence divergence of N. viennensis's 16s rRNA gene from its closest relative, Nitrososphaera gargensis, is 3%⁽³⁾.

Ammonia oxidizing Bacteria aerobically oxidize ammonia using ammonia monooxygenase (amoA) to catalyze the initial oxidation of NH₃⁽²⁾. Ammonia oxidizing Archaea have amo-like genes that may contribute to their ammonia oxidation⁽²⁾.

The urease gene cluster was located in one strain of N. viennensis, EN76⁽³⁾. The cluster consisted of the encoding subunits ureA, ureB, and ureC and the accessory proteins ureE, ureF, ureG, and ureD⁽³⁾.

NCBI: Genome

Metabolism

N. viennensis used urea or ammonia as an energy source in laboratory conditions⁽³⁾. It is able to grow chemolithoautotrohically with inorganic compounds as an electron donor, but displayed higher growth rates when grown with bacteria or with the addition of 0.1mM pyruvate⁽³⁾. It is currently unclear whether it is capable of heterotrophic or mixotrophic growth.⁽³⁾. The addition of vitamins, amino acids, and sugars had only a marginal effect on growth⁽³⁾. Acetylene is a possible growth inhibitor⁽³⁾.

Its optimal temperature is 35°C with an optimum pH of 7.5⁽³⁾. Generation time of a pure culture with 1mM ammonia and pyruvate was about ~45h⁽³⁾. Cell densities reached 5 X 10⁷ cells mL^-1(3). Growth on cultures with ammonium alone slowed down to ~23d demonstrating it can grow autotrophically exclusively although very slowly⁽³⁾.

It is able to withstand higher ammonia concentrations than other ammonia oxidizing archaea such as Nitrosopumilus maritimus and Nitrososphaera gargensis ⁽³⁾. Growth occurred at concentrations as high as 15 mM, but was inhibited at 20 mM⁽³⁾. Inhibitory ammonia concentrations for N. maritimus and N. gargensis are 2 to 3 mM. Ammonia tolerances were similar to some oligotrophic bacterial ammonia oxidizers associated with the Nitrosomonas oligotropha cluster⁽³⁾. However, other bacterial ammonia oxidizers have a much higher maximum ammonia tolerance of 50 to 1,000 mM⁽³⁾.

The electron transfer process is not fully understood yet in ammonia oxidizing archaea⁽²⁾. The amount of ATP per mole of NH₃ is unknown since it varies depending on growth stage and other factors⁽²⁾. Lack of cytochrome c proteins and many copper-containing proteins suggest a different electron transport mechanism than ammonia oxidizing bacteria, which is iron-heme-dependent⁽²⁾.

Ecology

N. viennensis exists in soil globally⁽²⁾. The first N. viennensis strain isolated was from garden soil from the University Center at Althanstrasse in Vienna's 9th District⁽⁴⁾.

Ammonia oxidizing Archaea such as N. viennensis may contribute to the nitrification of the environment⁽³⁾. It was previously believed only Bacteria could oxidize ammonia⁽³⁾. Ammonia oxidation is the first step in denitrification (NH₃ to NO_2-) ⁽²⁾. Eventually N₂O is produced in this process and escapes into the environment ⁽²⁾. N₂O has a greenhouse warming potential 310 times higher than CO₂⁽²⁾. It is responsible for 5%-7% of the greenhouse effect⁽²⁾. It is the third most important greenhouse gas after CO₂ and CH₄⁽²⁾. Ammonia oxidizing Bacteria and Archaea are estimated to contribute to ~70% of global N₂O emissions⁽²⁾.

Evidence shows that ammonia oxidizing Bacteria and Arachaea work together in mangrove forests in nitrogen cycling⁽¹⁾. These highly productive forests are important natural habitats for many marine organisms⁽¹⁾. Coastal ecosystems benefit from nutrient transformation and transport provided by ammonia oxidizing Bacteria and Archaea⁽¹⁾. Natural and man-made mangrove wetlands have been used as low cost way to treat municipal sewage with high amounts of inorganic nitrogen, which can be transformed by ammonia oxidizing Bacteria and Archaea⁽¹⁾.

References

1. Li, M., Cao, H., Hong, Y., and J. Gu (2011) Spatial distribution and abundances of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in mangrove sediments, Environmental Biotechnology 89: 1243-1254; doi: 10.1007/s00253-010-2929-0

2. Hatzenpichler, R. (2012) Diversity, physiology, and niche differentiation of ammonia-oxidizing archaea, Applied and Environmental Microbiology 2012 Nov: 78(21): 7501-10; doi: 10.1128/AEM.01960-12

3. Tourna, M., Stieglmeier, M., Spang, A., Könneke, M., Schintlmeister, A., Urich, T., Engel, M., Schloter, M., Wagner, M., Richter, A., and C. Schleper (2011) Nitrososphaera viennensis, an ammonia oxidizing archaeon from soil, PNAS 2011; doi:10.1073/pnas.1013488108

4. University of Vienna (2011) Novel microorganism 'Nitrososphaera viennensis' isolated. ScienceDaily, 2011 April 28. Retrieved April 28, 2013, from http://www.sciencedaily.com/releases/2011/04/110425153556.htm

Edited by Shanna Lovelace of Dr. Lisa R. Moore, University of Southern Maine, Department of Biological Sciences, http://www.usm.maine.edu/bio