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Methane oxidation and molecular characterization of methanotrophs from a former mercury mine impoundment

June 23, 2015

The Herman Pit, once a mercury mine, is an impoundment located in an active geothermal area. Its acidic waters are permeated by hundreds of gas seeps. One seep was sampled and found to be composed of mostly CO2 with some CH4 present. The δ13CH4 value suggested a complex origin for the methane: i.e., a thermogenic component plus a biological methanogenic portion. The relatively 12C-enriched CO2 suggested a reworking of the ebullitive methane by methanotrophic bacteria. Therefore, we tested bottom sediments for their ability to consume methane by conducting aerobic incubations of slurried materials. Methane was removed from the headspace of live slurries, and subsequent additions of methane resulted in faster removal rates. This activity could be transferred to an artificial, acidic medium, indicating the presence of acidophilic or acid-tolerant methanotrophs, the latter reinforced by the observation of maximum activity at pH = 4.5 with incubated slurries. A successful extraction of sterol and hopanoid lipids characteristic of methanotrophs was achieved, and their abundances greatly increased with increased sediment methane consumption. DNA extracted from methane-oxidizing enrichment cultures was amplified and sequenced for pmoA genes that aligned with methanotrophic members of the Gammaproteobacteria. An enrichment culture was established that grew in an acidic (pH 4.5) medium via methane oxidation.

Citation Information

Publication Year 2015
Title Methane oxidation and molecular characterization of methanotrophs from a former mercury mine impoundment
DOI 10.3390/microorganisms3020290
Authors Shaun Baesman, Laurence G. Miller, Jeremy H. Wei, Yirang Cho, Emily D. Matys, Roger E. Summons, Paula V. Welander, Ronald S. Oremland
Publication Type Article
Publication Subtype Journal Article
Series Title Microorganisms
Index ID 70159662
Record Source USGS Publications Warehouse
USGS Organization National Research Program - Western Branch