Methanosphaerula palustris

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Classification

Domain (archaea); Phylum (euryarchaeota); Class (methanomicrobia); Order (methanomicrobiales); most similar to the family Methanospirillaceae

Species

NCBI: Taxonomy

Methanosphaerula palustris

Description and Significance

Methanosphaerula palustris is a recently recognized species arising from research conducted through Cornell University in 2009. This research reported detailed information regarding the species' phylogenetic placement, physiology/morphology, and habitat from which it was isolated. Researchers utilized culture, microscopy, and molecular based techniques to describe the species' characteristics [1].

Methanosphaerula palustris was isolated from a rich, minerotrophic fen in New York state in 2008. M. palustris was cultured using a modified PM1 medium which is used for culturing anaerobic organisms such as this one. While growing at a range of pH values, a pH of 5.5 was determined to be optimal for growth. Preferred temperatures for growth were optimal at 30 degrees Celsius, giving it appropriately a mesophilic designation. M. palustris is a methanogen (methane producing) which apparently utilizes Hydrogen and Carbon dioxide as electron donors and acceptors respectively, along with acetate as a carbon source giving it the classification of chemolithoheterotroph.

Interestingly, although M. palustris is a member of the order Methanomicrobiales, an order documented as having significant physiological variability among members within it. Phylogenetic analysis using 16SrRNA and amino acid sequences indicates significant differences from other genera in this order, which has led to the proposition of Methanosphaerula as novel genus within Methanomicrobiales.

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 and Metabolism

Methanosphaerula palustris strain E1-9cT. Regular cocci cells associated in pairs with multiple flagella around. Photo by:Hinsby Cadillo-Quiroz, Joseph B. Yavitt & Stephen H. Zinder

The cells of the regular cocci, Gram-positive Archaea are mostly associated in pairs, 0.5-0.8 mm in size. While multiple flagella are grown with 14 nm thick and 8–12 mm length, they are readily lost under stress conditions such as high-speed centrifugation and oxic environments. Cell wall of the cells about 30–70 nm thick can be observed in thin sections under electron microscopy. As is shown in the study, cell walls can be resistant to SDS lysis, which indicates the cell wall is different from a single S-layer in spite of the fact that the S-layer is the only cell wall component in Archaea [2].

Methane is not produced from ethanol, methanol, 2-propanol, trimethylamine, 2-butanol, acetate, propionate or sodium butyrate, only using H2/CO2 or formate as substrates for methanogenesis in the strictly anaerobic condition. Na2S is used as a sulfur source. Growth will be inhibited with formate concentrations above 50 mM or Na2S concentrations above 0.1 mM.

Ecology

Like other members of the order Methanomicrobiales, M. palustris inhabits peat forming wetlands. These habitats occur sporadically in areas throughout the northern U.S and Canada. These habitats are typically acidic and anaerobic, which, along with the cooler temperatures, enables the extensive buildup of organic carbon. These habitats are understood to contribute significantly to the global flux of methane (CH4) [3], due in part to the metabolic action of methanogenic microbes such as M. palustris. Methane is the most abundant organic compound found in the atmosphere, and a potent greenhouse gas The EPA lists methane as having 21 C02 equivalents[4], giving it a high global warming potential (GWP). Drastic increases in atmospheric methane over the past several hundred years have put it at its highest estimated atmospheric concentration in over 400,000 years although this trend is largely attributed to human activitiy [5]. Commercially, these bogs are important sources of 'peat-moss'- a plant material that, after processing is slightly acidic, and capable of holding many times its weight in water making it an attractive component of soilless media used extensively in the horticultural industry.

References

[1]Cadillo-Quiroz, H et al. 2009. Methanosphaerula palustris gen. nov., sp. nov., a hydrogenotrophic methanogen isolated from a minerotrophic fen peatland. International Journal of Systematic and Evolutionary Microbiology 59: 928–935.

[2]Wikipedia http://en.wikipedia.org/wiki/S-layer

[3}Harriss, R. et al. Methane flux from northern peatlands. Nature 315, 652 - 654 (20 June 1985); doi:10.1038/315652a0

[4]Environmental Protection Agency. <epa.gov/climatechange/glossary.html>

[5]National Research Council. "Summary." Climate Change Science: An Analysis of Some Key Questions. Washington, DC: The National Academies Press, 2001. 1. Print.

Author

Page authored by Aaron Yoder, Shuya Zhang, and Justin Zhang, student of Prof. Jay Lennon at Michigan State University.

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