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

湿地土壤和沉积物中氧化-缺氧界面的生物甲烷氧化是甲烷循环的关键过程，可以防止大量温室气体逃逸到大气中。一种特殊的需氧细菌可以氧化甲烷，也可以吸收甲烷- c。在沼泽生态系统中，甲烷氧化细菌（MOB）负责大部分甲烷氧化，它们在海洋沉积物的表层也很重要。然而，甲烷化生物量的命运在很大程度上是未知的。我们证明了甲烷可以驱动整个微生物食物网。在土壤微观环境中，将一层水分饱和的稻田土壤在相反的氧气梯度和^ (13)c标记的甲烷下孵育，发现富含^ (13)c的“重”RNA，该RNA可能附属于MOB，清除原核黏菌，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MOB的选择性放牧。最近使用MOB作为模型的工作表明，微生物群落结构对生态系统功能很重要。结果表明，不仅要考虑微生物，而且要考虑原生生物多样性和微生物与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.