Metallosphaera sedula

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Classification

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

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Metallosphaera sedula, Gertrud et. al.


Species

NCBI: Taxonomy

Metallosphaera sedula

Description and Significance

Originally isolated from a volcanic field in Italy, Metallosphaera sedula can be roughly translated into “metal mobilizing sphere” with the word “sedulus” meaning busy, describing its efficiency in mobilizing metals. M. sedula is a highly thermoacidophilic Achaean that is unusually tolerant of heavy metals(1).

Due it its ability to ability to oxidize pyrite (FeS2), M. sedula has the potential to be used for coal depyritization (3). With increased awareness of the environmental impact of the combustion of coals, the idea of “clean coal” was born. While there are several focuses of “clean coal”, one of which is the removal of impurities, such as sulfur found in pyrite, prior to combustion. The combustion of sulfur leads to the formation of SO2, which has adverse health effects, and contributes to acid rain (4,5).

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Percent pyrite removal by M. sedula(black) and control (white). Clark et. al.

Abiotic removal of pyrite from coal is currently the preferred method, as opposed to biotic extraction via microorganisms; however, the process is feasible. Other organisms have been studied for the purpose of coal depyritization (for example, Thiobacillus ferroxidans), however the process occurs at a slower rate than traditional abiotic removal. (6) M. sedula, being thermophilic, is tolerant of higher temperatures which result in faster extraction rates than other organisms, and a strong candidate for future use in coal depyritization (3,6).

Genome Structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence?


Cell Structure, Metabolism and Life Cycle

M. sedula is a cocci, roughly 1um in diameter with pilus-like structures protruding from its surface when viewed via electron microscopy [1].

M. Sedula is an obligate aerobe that grows best at 75C and pH 2.0 [1]. The high level of physiological diversity it displaces is relatively unique amongst extremophiles. It is capable of heterotrophic growth using complex organic molecules (with the exception of sugars [1]), autotrophic growth by the fixation of carbon dioxide in the presence of H2 through an as yet unknown mechanism, and its highest rates of growth are seen when grown mixotropically on casamino acids and metal sulfides [2]. The dissimilatory oxidation of iron and sulfur in M. Sedula, driven by it by membrane oxidases, is key to M. sedula’s ability to mobilize metals and bioleach. When grown in the presence of H2, the ability of M. Sedula to leach copper from chalcopyrite (CuFeS2), is reduced [7].

Ecology and Pathogenesis

Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

References

1. Huber, G. ,Spinnler, C. , Gambacorta , A., and Stetter, K. “Metallosphaera sedula gen. and sp. nov. Represents a New Genus of Aerobic, Metal-Mobilizing, Thermoacidophilic Archaebacteria”. Systematic and Applied Microbiology. 1989. p. 38-47.
2. Auernik, K., and Kelly, R. “Physiological Versatility of the Extremely Thermoacidophilic Archaeon Metallosphaera sedula Supported by Transcriptomic Analysis of Heterotrophic, Autotrophic, and Mixotrophic Growth”. Applied and Environmental Microbiology. 2010. p. 931-935.
3. Clark, T., Baldi, F., And Olson, G. “Coal Depyritization by the Thermophilic Archaeon Metallosphaera sedula”. Applied and Environmental Microbiology. 1993. p. 2375-2379.
4. http://www.epa.gov/oaqps001/sulfurdioxide/
5. http://www.epa.gov/acidrain/what/index.html
6. Peeples, T.L., and Kelly, R.M., “Bioenergetics of the metal/sulfur-oxidizingextreme thermoacidophile, Metallosphaera sedula”. Fuel. 1993. p. 1577-1752.

Author

Page authored by Stephanie Napieralski and Caitlin Miller, students of Prof. Jay Lennon at Michigan State University.

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