Understanding endophyte communities of Echinacea purpurea to resolve plant medicinal efficacy

Background/Question/Methods

Echinacea purpurea is a native North American plant, whose medical use dates back to ancient indigenous people from several tribes. Despite its traditional use for anti-inflammatory (immuno-suppressive) properties, medical trials on the efficacy of plant extracts remain ambiguous. The effects of alkylamides, the active chemical compounds of the plant, appear to be counteracted by an immuno-stimulatory response triggered by lipopolysaccharides (LPS), which occur in cell walls of microorganisms. Recently, LPS presence in E. purpurea was linked to endophytic microorganisms rather than to contaminations during the extraction process. In this interdisciplinary study, teams including chemists, immunologists and ecologists investigate above and belowground relations between the plant and its endophytes. Microbial diversity of E. purpurea was assessed using tissue isolations from plants originating from three organic farms, Next Generations Sequencing and phylogeographic analyses. Isolates will be used for re-inoculations into endophyte free plants and their immuno-stimulatory activity will be evaluated by chemical extract profiles from the plant and their effects in immuno-assays.

Results/Conclusions

Isolations of seeds and roots yielded in more than 24 fungal and over 200 bacterial strains. Surface sterilized seeds harbored a majority of fungal isolates, which appear to be systemic. In contrast, root endophytes were predominantly consisting of bacteria, which suggests antifungal activity. Gram-negative rods were prevalent among bacterial isolates. Preliminary phylogenetic analyses have identified Paenibacillus spp. and Sphingomonas spp. as prokaryotic genera previously unknown to be associated to E. purpurea. This case study illustrates the importance of understanding the synecology of organisms to be able to determine the origin or key organisms responsible for the adverse effects to the desired medicinal properties of alkylamides present in E. purpurea.