Vandenkoornhuyse Philippe, Mahé Stéphane, Ineson Philip, Staddon Phil, Ostle Nick, Cliquet Jean-Bernard, Francez André-Jean, Fitter Alastair H, Young J Peter W
Centre National de la Recherche Scientifique, Unité Mixte de Recherche (UMR) 6553 EcoBio, IFR90/FR2116, Centre Armoricain de Recherche sur l'Environnement, Université de Rennes I, Campus de Beaulieu, 35042 Rennes Cedex, France.
Proc Natl Acad Sci U S A. 2007 Oct 23;104(43):16970-5. doi: 10.1073/pnas.0705902104. Epub 2007 Oct 15.
Plant roots harbor a large diversity of microorganisms that have an essential role in ecosystem functioning. To better understand the level of intimacy of root-inhabiting microbes such as arbuscular mycorrhizal fungi and bacteria, we provided (13)CO(2) to plants at atmospheric concentration during a 5-h pulse. We expected microbes dependent on a carbon flux from their host plant to become rapidly labeled. We showed that a wide variety of microbes occurred in roots, mostly previously unknown. Strikingly, the greatest part of this unsuspected diversity corresponded to active primary consumers. We found 17 bacterial phylotypes co-occurring within roots of a single plant, including five potentially new phylotypes. Fourteen phylotypes were heavily labeled with the (13)C. Eight were phylogenetically close to Burkholderiales, which encompass known symbionts; the others were potentially new bacterial root symbionts. By analyzing unlabeled and (13)C-enriched RNAs, we demonstrated differential activity in C consumption among these root-inhabiting microbes. Arbuscular mycorrhizal fungal RNAs were heavily labeled, confirming the high carbon flux from the plant to the fungal compartment, but some of the fungi present appeared to be much more active than others. The results presented here reveal the possibility of uncharacterized root symbioses.
植物根系中栖息着种类繁多的微生物，它们在生态系统功能中发挥着重要作用。为了更好地了解丛枝菌根真菌和细菌等根系微生物的亲密程度，我们在5小时的脉冲期间，以大气浓度向植物提供了（13）CO₂。我们预计依赖宿主植物碳通量的微生物会迅速被标记。我们发现根系中存在各种各样的微生物，其中大多数以前未知。引人注目的是，这种未被怀疑的多样性中最大的部分对应于活跃的初级消费者。我们在一株植物的根系中发现了17种共现的细菌系统型，包括5种潜在的新系统型。14种系统型被（13）C大量标记。其中8种在系统发育上与伯克霍尔德氏菌目相近，该目包含已知的共生体；其他的则可能是新的细菌根系共生体。通过分析未标记和（13）C富集的RNA，我们证明了这些根系微生物在碳消耗方面存在差异活性。丛枝菌根真菌的RNA被大量标记，证实了从植物到真菌部分的高碳通量，但存在的一些真菌似乎比其他真菌更活跃。这里呈现的结果揭示了未被表征的根系共生关系的可能性。
