Impact of copper geochemistry on the selection and abundance of methane-oxidizing bacteria in Arctic soils

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One of the most prominent signatures of climate change is progressively increasing levels of atmospheric methane (CH4). Although atmospheric carbon dioxide (CO2) levels are higher than CH4, CH4 has proportionally greater impact on heat retention within the atmosphere. Therefore, understanding what regulates and, more importantly, suppresses CH4 levels in the environment are of global significance. This is particularly pertinent to Arctic environments because as atmospheric warming continues, the rate of permafrost melting is increasing, resulting in the increased physical release of trapped CH4 from 'old' ice. As such, understanding better what regulates CH4 suppression in the Arctic is particularly critical to climate and is central to the work proposed here. CH4-oxidizing bacteria (methanotrophs) are nature's primary biological mechanism for reducing levels of atmospheric CH4, including CH4released from Arctic soils. However, methanotroph abundances within such soils appear lower than would be expected; although no good explanation has been provided why. Low numbers might simply result from low temperatures and-or short growing seasons, or they also might result from inadequate nutrient supplies especially copper (Cu). Cu is central to metabolism in methanotrophic bacteria because it is the metal-centre of particulate methane monooxygenase (pMMO), nature's most efficient enzyme at oxidising CH4. Further, laboratory results have shown that many methanotrophs produce small Cu-binding molecules, called methanobactins (mb), which mediate Cu acquisition for pMMO, especially from solid-phase geochemical Cu sources. Therefore, the scientific goal in this project is to extend and test our past laboratory results (and methods) related to Cu to the field to help explain CH4 oxidation patterns in the Arctic. This current proposal is fuelled by recent laboratory results that potentially explain how and when methanotrophs make mb to facilitate Cu uptake under different geochemical conditions (NE/F00608X/1) and a recent ARCFAC (27-2008) field reconnaissance visit to Ny-Alesund, Svalbard. Evidence from NE/F00608X/1 work has shown that mb is made by non-ribosomal peptide synthetase cassettes, and we are currently testing RT-PCR probe-primer set(s) to quantify mb manufacture as a potential environmental sample-screening tool. Alternately, the ARCFAC visit, which was with experts from the United States, Norway, and Germany, identified eight potentially contrasting sites in terms of Cu and CH4 conditions within 6 km of Ny-Alesund. ARCFAC reconnaisance data also showed moisture, nitrogen (N), temperature, and CH4 levels were also important in methanotroph selection. Therefore, our goal in this new NERC project is to return to Ny-Alesund during summer 2009 to field-test our new mb probes at differing sites to test if Cu geochemistry, other habitat factors (e.g., N and CH4 levels), and mb expression patterns might explain the inexplicable patterns of methanotrophic activity in Arctic soils. This proposal will have significant added-value because the work will be performed in concert with an international group of outside experts who are part of the larger ARCFAC research team (which we lead). Specifically, each group will contribute their skills and resources to a larger effort with this proposal initially funding our component. It is planned, however, that as we gather more information about methanotroph ecology in the Arctic through work next summer, much larger proposals will be prepared, both domestically and internationally, to support future collaborative activities.