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

湿地土壤和沉积物中氧-缺氧界面上的甲烷生物氧化是甲烷循环中的一个关键过程，可以防止这种温室气体大量逃逸到大气中。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，甲烷氧化细菌(MOB)是甲烷氧化的主要原因，它们在海洋沉积物的表层也很重要。然而，甲烷营养生物质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链可以由甲烷驱动。土壤微宇宙中，一层薄薄的饱和水分的稻田土壤在相反的氧气和~(13)C标记甲烷的梯度下孵化，揭示了~(13)C富含“重”RNA，它可能附属于暴徒、食腐的原核粘细菌，以及包括变形虫、纤毛虫和鞭毛虫在内的原生食草动物。不同的原生生物群落的发展取决于甲烷浓度。从土壤中分离出来的原生生物表现出对暴徒的选择性捕食。最近以MOB为模型的研究表明，微生物群落结构对生态系统的功能很重要。结果表明，不仅要考虑微生物，还要考虑原生生物的多样性和微生物-原生生物的相互作用。

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.