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

气候变化最显著的特征之一是大气甲烷（CH 4）水平逐渐增加。虽然大气中的二氧化碳（CO2）含量高于CH 4，但CH 4对大气中的热量保持的影响更大。因此，了解是什么调节，更重要的是，抑制环境中的CH 4水平具有全球意义。这与北极环境特别相关，因为随着大气变暖的持续，永久冻土融化的速度正在增加，导致从“老”冰中捕获的CH 4的物理释放增加。因此，更好地了解是什么调节了北极地区的甲烷抑制，对气候特别重要，也是这里提出的工作的核心。甲烷氧化菌（甲烷氧化菌）是自然界减少大气中甲烷含量的主要生物机制，包括北极土壤释放的甲烷。然而，甲烷氧化菌丰度在这样的土壤中出现低于预期，虽然没有很好的解释已经提供了为什么。低数量可能仅仅是由于低温和-或生长季节短，或者也可能是由于营养供应不足，特别是铜（Cu）。铜是甲烷氧化细菌代谢的核心，因为它是颗粒甲烷单加氧酶（pMMO）的金属中心，pMMO是自然界氧化CH 4最有效的酶。此外，实验室结果表明，许多甲烷氧化菌产生小的铜结合分子，称为甲烷氧化菌素（MB），介导铜收购pMMO，特别是从固相地球化学铜源。因此，本项目的科学目标是将我们过去与Cu相关的实验室结果（和方法）扩展和测试到该领域，以帮助解释北极的CH 4氧化模式。最近的实验室研究结果可能解释甲烷氧化菌如何以及何时产生甲烷，以促进不同地球化学条件下的铜吸收（NE/F00608 X/1）和最近的ARCFAC（27-2008）现场勘察访问斯瓦尔巴群岛的Ny-Alesund。来自NE/F00608 X/1工作的证据表明，mb是由非核糖体肽合成酶盒产生的，我们目前正在测试RT-PCR探针-引物组，以定量mb的产生，作为一种潜在的环境样品筛选工具。另一方面，ARCFAC的访问，这是与来自美国，挪威和德国的专家，确定了八个潜在的对比地点在Cu和CH 4的条件下在6公里内的新奥勒松。ARCFAC的调查数据还表明，水分，氮（N），温度和甲烷氧化菌的选择也很重要。因此，我们在这个新的NERC项目中的目标是在2009年夏天返回新奥勒松，在不同的地点实地测试我们的新mb探针，以测试铜的地球化学，其他栖息地因素（例如，N和CH 4水平），和MB的表达模式可能解释了在北极土壤中的甲烷氧化活性的莫名其妙的模式。该提案将具有重要的附加值，因为这项工作将与一个国际外部专家小组合作进行，这些专家是更大的ARCFAC研究团队（由我们领导）的一部分。具体来说，每个小组将贡献他们的技能和资源，以更大的努力与本提案最初资助我们的组成部分。然而，随着我们明年夏天通过工作收集更多关于北极甲烷氧化菌生态的信息，计划在国内和国际上准备更大的提案，以支持未来的合作活动。

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.