Bacterial communities exposed to Benzoxazinoids

Plants synthesize and release specialized metabolites into their environment that can serve aschemical cues for other organisms. Metabolites that are released from the roots are importantfactors in determining which microorganisms will colonize the root and become part of the plantrhizosphere microbiota. Root exudates are often further converted by soil microorganisms,which can result in the formation of toxic compounds. How individual members of the plantrhizosphere respond to individual compounds and how the differential response of individualmicroorganisms contributes to the response of a microbial community remains unclear. Here,we investigated the impact of derivatives of one class of plant root exudates, benzoxazinoids,which are released by important crops such as wheat and maize, on a collection of 180 rootassociatedbacteria. We show that phenoxazine, derived from benzoxazinoids, inhibits thegrowth of root-associated bacteria in vitro in a strain-specific manner, with sensitive andresistant isolates in most of the studied clades. Synthetic bacterial communities that wereassembled from only resistant isolates were more resilient to chemical perturbations thancommunities comprised of only sensitive members. Isolates that were shared between differentcommunities revealed stable interactions, independent of the overall community composition.On the other hand, we could attribute differential community development to differences ininteractions formed by closely related representatives of the same bacterial genus. Our findingshighlight the fact that profiling isolate collections can aid the rational design of syntheticcommunities. Moreover, our data show that simplified in vitro community systems are able torecapitulate observations on the influence of metabolite exudation on the structure of rootassociatedcommunities, thus providing an avenue for reductionist explorations of therhizosphere biology in defined, host-free settings.