Microbial Communities in Subpermafrost Saline Fracture Water at the Lupin Au Mine, Nunavut, Canada

We report the first investigation of a deep subpermafrost microbial ecosystem, a terrestrial analog for the Martian subsurface. Our multidisciplinary team analyzed fracture water collected at 890 and 1,130 m depths beneath a 540-m-thick permafrost layer at the Lupin Au mine (Nunavut, Canada). ¹⁴C, ³...

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Bibliographic Details
Published in:	Environmental microbiology Vol. 58; no. 4; pp. 786 - 807
Main Authors:	Onstott, T. C, McGown, Daniel J, Bakermans, Corien, Ruskeeniemi, Timo, Ahonen, Lasse, Telling, Jon, Soffientino, Bruno, Pfiffner, Susan M, Sherwood-Lollar, Barbara, Frape, Shaun, Stotler, Randy, Johnson, Elizabeth J, Vishnivetskaya, Tatiana A, Rothmel, Randi, Pratt, Lisa M
Format:	Journal Article
Language:	English
Published:	New York New York : Springer-Verlag 01-11-2009 Springer Science + Business Media, Inc Springer-Verlag Springer Nature B.V
Subjects:	ABUNDANCE Aerobic bacteria Anaerobic bacteria Archaea BACTERIA Bacteria - classification Bacteria - genetics Bacteria - isolation & purification BASIC BIOLOGICAL SCIENCES Biodiversity Biomedical and Life Sciences Brines CARBOXYLIC ACIDS COMMUNITIES Community composition Deglaciation DENITRIFICATION Dewatering DNA DNA, Bacterial - genetics Ecology Ecosystem ECOSYSTEMS ENVIRONMENTAL MICROBIOLOGY ENVIRONMENTAL SCIENCES FRACTURES FREE ENERGY GENES Geoecology/Natural Processes GROUND WATER Groundwater Halothiobacillus Life Sciences Lipids - analysis Lupin Au Mine Meteoric water Methane Methanogenesis Microbial activity Microbial communities Microbial Ecology Microbiology Mining Nature Conservation Nunavut Original Article OXIDATION PERMAFROST Phylogeny Pleistocene Polymerase chain reaction Product category rules PSEUDOMONAS Pyrite Quinones RNA, Ribosomal, 16S - genetics Saltwater Soil Microbiology subpermafrost Sulfate reduction SULFATE-REDUCING BACTERIA Sulfates Sulfides Sulfur Sulfur - analysis SULFUR ISOTOPES UBIQUINONE WATER Water - analysis Water - chemistry Water Microbiology Water Quality/Water Pollution WATER REMOVAL Nunavut Canada, Nunavut Fracture Water Sulfur Isotopic Composition Borehole Water SO42 Multiple Displacement Amplification
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Summary:	We report the first investigation of a deep subpermafrost microbial ecosystem, a terrestrial analog for the Martian subsurface. Our multidisciplinary team analyzed fracture water collected at 890 and 1,130 m depths beneath a 540-m-thick permafrost layer at the Lupin Au mine (Nunavut, Canada). ¹⁴C, ³H, and noble gas isotope analyses suggest that the Na-Ca-Cl, suboxic, fracture water represents a mixture of geologically ancient brine, ~25-kyr-old, meteoric water and a minor modern talik-water component. Microbial planktonic concentrations were ~10³ cells mL⁻¹. Analysis of the 16S rRNA gene from extracted DNA and enrichment cultures revealed 42 unique operational taxonomic units in 11 genera with Desulfosporosinus, Halothiobacillus, and Pseudomonas representing the most prominent phylotypes and failed to detect Archaea. The abundance of terminally branched and midchain-branched saturated fatty acids (5 to 15 mol%) was consistent with the abundance of Gram-positive bacteria in the clone libraries. Geochemical data, the ubiquinone (UQ) abundance (3 to 11 mol%), and the presence of both aerobic and anaerobic bacteria indicated that the environment was suboxic, not anoxic. Stable sulfur isotope analyses of the fracture water detected the presence of microbial sulfate reduction, and analyses of the vein-filling pyrite indicated that it was in isotopic equilibrium with the dissolved sulfide. Free energy calculations revealed that sulfate reduction and sulfide oxidation via denitrification and not methanogenesis were the most thermodynamically viable consistent with the principal metabolisms inferred from the 16S rRNA community composition and with CH₄ isotopic compositions. The sulfate-reducing bacteria most likely colonized the subsurface during the Pleistocene or earlier, whereas aerobic bacteria may have entered the fracture water networks either during deglaciation prior to permafrost formation 9,000 years ago or from the nearby talik through the hydrologic gradient created during mine dewatering. Although the absence of methanogens from this subsurface ecosystem is somewhat surprising, it may be attributable to an energy bottleneck that restricts their migration from surface permafrost deposits where they are frequently reported. These results have implications for the biological origin of CH₄ on Mars.
Bibliography:	http://dx.doi.org/10.1007/s00248-009-9553-5 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 DE-AC05-00OR22725 USDOE Office of Science (SC)
ISSN:	0095-3628 1462-2912 1432-184X 1462-2920
DOI:	10.1007/s00248-009-9553-5