Genetic Characterisation of the Bacterial Microbiota Associating With a Strain of Epichloë Fungal Endophyte of Perennial Ryegrass and the Interaction With Its Paenibacillus Members

Abstract

Plant-associated fungi can host unique bacterial microbiota to provide multiple benefits to their fungal hosts. Here it was characterised the bacterial microbiota associated with an Epichloë fungal endophyte (strain AR135) isolated from perennial ryegrass (Lolium perenne) via both 16S rRNA gene sequencing and direct microbial isolation and investigated the microbe-microbe interactions between these bacteria and the fungus. The bacterial microbiota of AR135 was dominated by members within the genus Paenibacillus, with 99% of abundance (on average); although bacteria within genera Delftia and Bradyrhizobium were also present. Paenibacillus cells were located on the surface of hyphae of AR135 fungus in vitro on synthetic media and in planta within perennial ryegrass leaves. Two bacterial strains, E100 and E300, identified as Paenibacillus, were isolated from the AR135 mycelium. E300 drastically altered the abundance of both the whole bacterial microbiota (increased by 63%) and E100 (reduced to 0%). None of the variations observed in the abundance of total bacterial microbiota and E100 and E300 were associated with changes in the fungal biomass of Epichloë. The findings show that Epichloë fungal endophytes can host bacterial communities, the structure of which was regulated by key members of the bacterial community.