Riverbed methanotrophy sustained by high carbon conversion efficiency.
Riverbed methanotrophy sustained by high carbon conversion efficiency.
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DOI：
10.1038/ismej.2015.98
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发表时间：
2015-10
期刊：
影响因子：
--
通讯作者：
Grey J
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文献类型：
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作者：
Trimmer M;Shelley FC;Purdy KJ;Maanoja ST;Chronopoulou PM;Grey J
我们对淡水在全球碳循环中所起作用的认识正在修订，但仍然缺乏数据，特别是关于河流和溪流中甲烷循环的数据。解开甲烷化作用是决定河流中甲烷命运的关键。在这里，我们关注甲烷化的碳转化效率（CCE），即每摩尔氧化CH4产生多少有机碳，以及这是如何受到甲烷化菌群落变化的影响的。首先，我们发现河床甲烷氧化菌的CCE在很宽的甲烷浓度范围内（~ 10-7000 nM）始终很高（~50%），尽管甲烷氧化速率跨度为10倍。然后，我们发现这种高转化效率在关键功能基因（70个操作分类单位（OTUs））、颗粒甲烷单加氧酶（pmoA）的显著变化以及8个重复白垩溪流中I型和II型甲烷氧化菌丰度的显著变化中在很大程度上是保守的（50%±置信区间44-56%）。这些数据可能表明，在居住在这些河流中的可变甲烷化菌群落中存在一定程度的功能冗余，并且pmoA的一些变化可能反映了一套不同甲烷亲和力的酶，这些酶使如此大范围的甲烷浓度能够被氧化。后者，加上它们的高CCE，使甲烷氧化菌能够全年维持净产量，而不管甲烷发生明显的时间和空间变化。
Our understanding of the role of freshwaters in the global carbon cycle is being revised, but there is still a lack of data, especially for the cycling of methane, in rivers and streams. Unravelling the role of methanotrophy is key to determining the fate of methane in rivers. Here we focus on the carbon conversion efficiency (CCE) of methanotrophy, that is, how much organic carbon is produced per mole of CH4 oxidised, and how this is influenced by variation in methanotroph communities. First, we show that the CCE of riverbed methanotrophs is consistently high (~50%) across a wide range of methane concentrations (~10–7000 nM) and despite a 10-fold span in the rate of methane oxidation. Then, we show that this high conversion efficiency is largely conserved (50%± confidence interval 44–56%) across pronounced variation in the key functional gene (70 operational taxonomic units (OTUs)), particulate methane monooxygenase (pmoA), and marked shifts in the abundance of Type I and Type II methanotrophs in eight replicate chalk streams. These data may suggest a degree of functional redundancy within the variable methanotroph community inhabiting these streams and that some of the variation in pmoA may reflect a suite of enzymes of different methane affinities which enables such a large range of methane concentrations to be oxidised. The latter, coupled to their high CCE, enables the methanotrophs to sustain net production throughout the year, regardless of the marked temporal and spatial changes that occur in methane.