Analysis of the microbial food web in a wetland soil diiven by methane oxidation

湿地土壤和沉积物中缺氧-缺氧界面的甲烷生物氧化是甲烷循环的关键过程，阻止了大量这种温室气体逃逸到大气中。一组特定的好氧细菌氧化甲烷，也能够同化甲烷-C。在湖泊生态系统中，甲烷氧化菌（MOB）承担着大部分甲烷氧化作用，在海洋沉积物表层也有重要作用。然而，甲烷氧化生物量的命运在很大程度上是未知的。我们证明了整个微生物食物网可以由甲烷驱动。在土壤微宇宙中，将一薄层水饱和的稻田土壤置于氧气和^（13）C标记的甲烷的相反梯度下培养，发现富含^（13）C的"重" RNA可能与MOB、原核粘细菌和原生生物（包括变形虫、纤毛虫和鞭毛虫）有关。不同的原生生物群落的发展取决于甲烷浓度。从土壤中分离的原生生物表现出选择性放牧MOB。最近的工作使用MOB作为一个模型表明，微生物群落结构的生态系统功能的事项。结果表明，不仅微生物，但也原生生物多样性和微生物-原生生物相互作用必须考虑。

Biological methane oxidation at the oxic-anoxic interface in wetland soils and sediments is a key process in methane cycle, preventing large amounts of this greenhouse gas to escape into the atmosphere. A specific group of aerobic bacteria oxidises methane and is also able to assimilate methane-C. In limnic ecosystems, MOB (methane oxidising bacteria) are responsible for most of the methane oxidation, and they are also important in the surface layer of marine sediments. However, the fate of methanotrophic biomass is largely unknown. We demonstrate that an entire microbial food web can be driven by methane. Soil microcosms, in which a thin layer of water-saturated rice field soil was incubated under opposing gradients of oxygen and ^ (13) C-labelled methane, revealed ^ (13) C-enriched "heavy" RNA which could be affiliated to MOB, to the scavenging prokaryotic Myxobacteria, and to protistan grazers including amoebae, ciliates, and flagellates. Different protistan communities developed depending on methane concentrations. Protists isolated from the soil demonstrated selective grazing on MOB. Recent work using MOB as a model has shown that microbial community structure matters for ecosystem functioning. The results suggest that not only microbial, but also protistan diversity and microbe-protist interactions have to be considered.