Isolation and Characterization of Methanotrophic Bacteria from a Subglacial Antarctic Lake

Lindsey Kuchenbecker

Authors:  Lindsey Kuchenbecker

Faculty Mentor:  Brent Christner

College:  College of Agricultural and Life Sciences


Methane is a potent greenhouse gas with 30-times the heat trapping capacity of CO2. Methanotrophs are microorganisms that use methane carbon for biomass and oxidize it to carbon dioxide as a metabolic byproduct. Mercer Subglacial Lake (SLM), West Antarctica is an aquatic environment that exists beneath ~1100 m of ice and contains a microbial community in which methane is cycled within in the aerobic water column and surficial sediments (0-30 cm). Enrichment cultures containing methane that were analyzed by gas chromatography identified samples in which methane oxidation had occurred. From these samples, methane oxidizing bacteria were isolated using minimal nitrate mineral salts media amended with methane as the sole carbon source. Amplification and sequencing of the particulate methane monooxygenase (pMOA) gene was used to identify various methanotrophic strains within the genera Methylomonas and isolate them in pure culture. Methanotrophs in environments beneath ice sheets are poorly understood, yet they have the potential to have an important impact on mitigating the release of methane in runoff and during deglaciation. Elucidating the characteristics of these bacteria can provide insight on how carbon is cycled beneath the West Antarctica Ice Sheet and their role as a biological sink for methane.

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7 Responses
  1. Brent Christner

    Lindsey – excellent job on the youtube presentation. I was wondering if you noticed that your isolates appear most closely related to Methylomonas denitrificans, which is a species that has been shown to oxidized methane with nitrate, producing nitrous oxide (another potent greenhouse gas). Can you think of a way to test the ability of your strains to use nitrate as an alternative electron acceptor? Nice work!

    1. Lindsey Kuchenbecker

      Brent – Great question! I think one way to test the ability of my samples to use nitrate as an alternative electron acceptor would be to inoculate samples, that are otherwise identical, with different ratios of nitrates. From there I could use gas chromatography to determine the rate of nitrate metabolism or nitrous oxide production.

      1. Brent Christner

        That would be a way to do it. Not sure what the N source is is the media, but if there is nitrate it is possible some of your older cultures that have depleted the O2 have switched to nitrate respiration without us knowing it. Since Adrian has been working with Jon Martin and his student Madison Flint to look at N2O in the springs, it would be easy to test some of your culture headspaces to see if there was any N2O. Good stuff!