Ectomycorrhizal fungi live in close association with their host plants and form complex interactions with bacterial/archaeal communities in soil. We investigated whether abundant or rare ectomycorrhizal fungi on root-tips of young beech trees (Fagus sylvatica) shape bacterial/archaeal communities. We sequenced 16S rRNA genes and fungal internal transcribed spacer regions of individual root-tips and used ecological networks to detect the tendency of certain assemblies of fungal and bacterial/archaeal taxa to inhabit the same root-tip (i.e. modularity). Individual ectomycorrhizal root-tips hosted distinct fungal communities associated with unique bacterial/archaeal communities. The structure of the fungal-bacterial/archaeal association was determined by both, dominant and rare fungi. Integrating our data in a conceptual framework suggests that the effect of rare fungi on the bacterial/archaeal communities of ectomycorrhizal root-tips contributes to assemblages of bacteria/archaea on root-tips. This highlights the potential impact of complex fine-scale interactions between root-tip associated fungi and other soil microorganisms for the ectomycorrhizal symbiosis.

外生菌根真菌与其寄主植物密切相关，并与土壤中的细菌/古细菌群落形成复杂的相互作用。我们调查了幼年山毛榉树 ( Fagus sylvatica ) 根尖上的外生菌根真菌是丰富还是稀少) 塑造细菌/古细菌群落。我们对单个根尖的 16S rRNA 基因和真菌内部转录间隔区进行了测序，并使用生态网络来检测某些真菌和细菌/古生菌类群聚集在同一根尖的趋势（即模块性）。单个外生菌根根尖承载着与独特的细菌/古菌群落相关的不同真菌群落。真菌-细菌/古细菌联合体的结构由显性真菌和稀有真菌共同决定。将我们的数据整合到一个概念框架中表明，稀有真菌对外生菌根根尖的细菌/古细菌群落的影响有助于根尖上细菌/古细菌的组合。