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Abstract

The symbiosis between tall fescue (Festuca arundinaceum) and a shoot-specificÌýfungal endophyte (Neotyphodium coenophialum) has been relatively well studied butÌýlittle attention has been given to how this relationship may impact the soil microbialÌýcommunity. Understanding how the symbiosis may structure soil microbial communitiesÌýis important for understanding the cascade of effects that this symbiosis can have onÌýbelowground ecosystems. We used high-throughput DNA sequencing of selectedÌýmicrobial genes (the 16S rRNA gene and fungal ITS rRNA region) to examine bacterialÌýand fungal microbial communities in the soil, respectively, to address the followingÌýquestions: (1) How do the microbial communities differ between rhizosphere and bulkÌýsoil in a tall fescue grassland? (2) How are belowground microbial communities affectedÌýby the presence of various strains of endophyte N. coenophialum? We found thatÌýrhizosphere and bulk soils harbored distinct microbial communities, with rhizosphereÌýcommunities containing significantly higher relative abundances of Bacteroidetes, α-Ìý±Ê°ù´Ç³Ù±ð´Ç²ú²¹³¦³Ù±ð°ù¾±²¹, β-Proteobacteria, γ-proteobacteria, and Chytridiomycota, while bulk soilÌýcontained higher relative abundances of Verrucomicrobia, Acidobacteria, Firmicutes, andÌýZygomycota. We also found that endophyte presence significantly influenced rhizosphereÌýmicrobial communities, with a greater effect on fungal versus bacterial communities. InÌýparticular, we observed an increased relative abundance of root-associated (arbuscularÌýmycorrhizal) fungi in fescue plants containing shoot fungal endophytes. Our dataÌýsuggests a complex, tripartite interaction between shoot endophytes, tall fescue and rootÌýassociated fungi, which could have greater implications for grassland soils.