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Abstract

The symbiosis between tall fescue (Festuca arundinaceum) and a shoot-specific fungal endophyte (Neotyphodium coenophialum) has been relatively well studied but little attention has been given to how this relationship may impact the soil microbial community. Understanding how the symbiosis may structure soil microbial communities is important for understanding the cascade of effects that this symbiosis can have on belowground ecosystems. We used high-throughput DNA sequencing of selected microbial genes (the 16S rRNA gene and fungal ITS rRNA region) to examine bacterial and fungal microbial communities in the soil, respectively, to address the following questions: (1) How do the microbial communities differ between rhizosphere and bulk soil in a tall fescue grassland? (2) How are belowground microbial communities affected by the presence of various strains of endophyte N. coenophialum? We found that rhizosphere and bulk soils harbored distinct microbial communities, with rhizosphere communities containing significantly higher relative abundances of Bacteroidetes, α- Proteobacteria, β-Proteobacteria, γ-proteobacteria, and Chytridiomycota, while bulk soil contained higher relative abundances of Verrucomicrobia, Acidobacteria, Firmicutes, and Zygomycota. We also found that endophyte presence significantly influenced rhizosphere microbial communities, with a greater effect on fungal versus bacterial communities. In particular, we observed an increased relative abundance of root-associated (arbuscular mycorrhizal) fungi in fescue plants containing shoot fungal endophytes. Our data suggests a complex, tripartite interaction between shoot endophytes, tall fescue and root associated fungi, which could have greater implications for grassland soils.