Metallosphaera cuprina

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Classification

Domain: Archaea
Phylum: Crenarchaeota
Class: Thermoprotei
Order: Sulfolobales
Family: Sulfolobaceae
Genus: Metallosphaera

Description and Significance

Metallosphaera cuprina was originally isolated from muddy hot spring water in the Yunnan province of China and is named in reference to copper, cuprina, due to the extraction of copper from ores near the hotspring. [1]

M. cuprina differs from other species of Metallosphaera as it is more extermophilic and can grow in lower temperatures and higher pH than most. M. cuprina grows best at 65°C, and pH 3.5, but can grow in ranges of 0-1% (w/v) NaCl, 55-75° C, and pH 2.5-5.5. [1]

There is potential for the use of M. cuprina and other Metallosphaera in the mining industry through bioleaching, due to its oxidation of reduced inorganic sulfur compounds. [2] Bacteria are typically used to further oxidize Fe³⁺-oxidized ore, and regenerate Fe²⁺. [15]

Genome Structure and Phylogeny

Phylogenetic tree of Metallosphaera cuprina and related species [14]

The M. cuprina genome is 1.84Mb [2] and contains 2077 genes [9]. In comparison, Metallosphaera sedula has a 2.19 Mb genome and 2307 genes [11], making the M. cuprina genome16% smaller than M. sedula.
The Ar-4^T strain of M. cuprina has a GC content of 40.2 mol%. This is slightly lower than other Metallosphaera species: M. sedula, 46.2 mol% [8]; and Metallosphaera hakonensis, 46.2 mol%[10]; Metallosphaera prunae, 46 mol%[4].
This strain shares sequence similarities of 97.7% with M. hakonensis DSM 7519^T, 97.0% with M. sedula DSM 5348^T, and 96.8% with M. prunae DSM 10039^T. [1] Through 16S rRNA gene sequence analysis, it is observed that M. cuprina shares less than 90% similarities with the [1]Acidianus genera, and less than 88% similarities with the Sulfolobus genera. [1]

Cell Structure, Metabolism and Life Cycle

M. cuprina is a Gram-negative, irregular cocci of 0.9-1.0µm diameter [1]. Like M. prunae[4] but not M. hakonensis or M. sedula [1][5][10], M. cuprina has flagella and is motile [4]. The flagella of M. cuprina are long and curved. [1]]

When grown on potassium tetrathionate-supplemented “Allen” plates, M. cuprina appears as rounded, convex colonies between 0.2-0.3 mm with a semi-transparent and smooth appearance. When supplemented with FeSO₄ instead of potassium tetrathionate, the colonies are brown and flat. [1]

Its cellular lipids are mainly composed of calditoglycerocaldarchaeol and caldarchaeol—the same core lipids that are also present in M. sedula, M. hakonensis, and S. acidocaldarius [1]. Caldarchaeol provide stability to the cell membrane and are present in many hyperthermophilic archaea. While calditoglycerocaldarchaeol is also present in many Sulfolobales, it might not be required for survival in thermoacidophilic environments. [12]

M. cuprina is an aerobic and facultatively chemolithoautotrophic species also capable of organotrophic growth on various organic materials. M. cuprina is able to use sulfidic ore as a source of metal ions, in addition to oxidizing reduced sulfur compounds. [1] Therefore, along with M. sedula, M. cuprina has a good degree of physiological versatility [7]. M. cuprina is capable of chemolithoautotrophic growth using elemental sulfur, K₂S₄O₆, and FeSO₄. Similar to most reported members of the Metallosphaera genus, M. cuprina is capable of using tetrationate and pyrite or FeS as sulfur sources; L-Aspartic acid, L-Glutamic acid, L-Tryptophan, and L-Alanine as amino acid sources; and yeast extract, beef extract, peptone, tryptone, and Casamino acids as organic substrates. Unlike its fellow genus members, M. cuprina is capable of using L-Arabinose, D-Xylose, D-gGlucose, sucrose, and raffinose as sugars. As in M. sedula, M. cuprina is incapable of using D-Mannose for sugars. [1]

M. cuprina has a complete TCA cycle and an incomplete pentose phosphate pathway. [2]

Ecology

Metallosphaera cuprina was originally isolated from sulfuric hot springs in Yunnan, China. [1] The isolation of this organism from an extreme environment is in line with others of the genus, which were originally isolated from heated waste matter from a mine [4], a hot spring [5], and a sulfurous volcanic field [6]. As M. cuprina was found in a sulfur hot spring, and found able to grow in temperatures up to 75°C and pH as low as 2.5, it can be considered an acidothermophile. [1]

Polyphosphates are present in all types of cells and are known to act as a phosphate and energy source, and a regulator of various cellular processes such as ATP regulation [13]. Inorganic polyphosphate has been proposed as a mechanism for the resistance of M. cuprina and other extremeophiles to the extreme conditions that they encounter, such as high metals, salt, and temperature. [3]

References

1. Liu, L.J., You, X.Y., Guo, X., Liu, S.J., Jiang, C.Y. “Metallosphaera cuprina sp. nov., an acidothermophilic, metal-mobilizing archaeon.” IJSEM, 2011, DOI: 10.1099/ijs.0.026591-0.
2. Liu, L.J., You, X.Y., Zheng, H., Wang, S., Jiang, C.Y., Liu, S. “Complete Genome Sequence of Metallosphaera cuprina, a Metal-Sulfide Oxidizing Archaeon from a Hot Spring.”J Bacteriol, 2011, DOI: 10.1128/JB.05038-11.
3. Orell, A., Navarro, C.A., Rivero, M., Aguilar, J.S., Jerez. C.A. “Inorganic polyphosphates in extremophiles and their possible functions.” Extremophiles, 2012, DOI: 10.1007/s00792-012-0457-9.
4. Fuchs, T., Huber, H., Teiner, K., Burggraf, S., Stetter, K.O. “Metallosphaera prunae, sp. nov., a Novel Metal-mobilizing, Thermoacidophilic Archaeum, Isolated from a Uranium Mine in Germany”. Systematic and Applied Microbiology, 1995, DOI: 10.1016/S0723-2020(89)80038-47.
5. Takayanagi, S., et. al. “Sulfolobus hakonensis sp. nov., a Novel Species of Acidothermophilic Archaeon”. IJSEM, 1996, DOI: 10.1099/00207713-46-2-377.
6. Huber, G., Spinnler, C., Gambacorta, A., Stetter, K.O. “Metallosphaera sedula gen, and sp. nov. Respresents a New Genus of Aerobic, Metal-Mobilizing, Thermoacidophilic Archaebacteria”. Systemic and Applied Microbiology, 1989, DOI: 10.1016/S0723-2020(89)80038-4.
7. Auernik, K.S., Maezato, Y., Blum, P.H., Kelly, R.M., “The genome sequence of the metal-mobilizing, extremely thermoacidophilic archaeon Metallosphaera sedula provides insights into bioleaching-associated metabolism.” Appl Environ Microbiol, 2008, PMID: 18083856.
8. Metallosphaera sedula DSM 5348
9. KEGG GENOME: Metallosphaera cuprina.
10. Kurosawa, N., Itoh, Y.H., Itoh, T. “Reclassification of Sulfolobus hakonensis Takayanagi et al. 1996 as Metallosphaera hakonensis comb. nov. based on phylogenetic evidence and DNA G+C content”. IJSEM, 2003, DOI: 10.1099/ijs.0.02716-0.
11. KEGG GENOME: Metallosphaera sedula.
12. Itoh, Y.H., et. al. “Metallosphaera sedula TA-2, a calditoglycerocaldarchaeol deletion strain of a thermoacidophilic archaeon”. Extremophiles, 2001, DOI: 10.1007/s007920100195.
13. Kulaev, I., Vagabov, V., Kulakovskaya, T. “New aspects of inorganic polyphosphate metabolism and function”. Journal of Bioscience and Bioengineering, 1999, DOI: 10.1016/S1389-1723(99)80189-3.
14. http://microbes.ucsc.edu/cgi-bin/hgGateway?org=Metallosphaera+cuprina+Ar+4&db=metaCupr1&hgsid=649090
15. Bioleaching

Author

Page authored by J. Wibowo, student of Dr. Bill Mohn at the University of British Columbia.

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