Evolutionarily Conserved Core Rhizosphere Microbiota Promotes Host Performance and Fitness in Heavy Metal Accumulating Plants

Background: Persistent microbial symbioses offer the potential to confer greater fitness to the host under unfavorable conditions, but manipulation of such beneficial interactions requires a mechanistic understanding of the consistently important microbiome members for the plant. Here, use five phylogenetically divergent heavy metal (HM) accumulating plants as a model, we examined the composition, assembly and relationships of the core and active rhizosphere microbiota across diverse soils with varying concentrations of HMs and further explored their roles in host performance.Results: Our results showed that the rhizosphere bacterial communities were primarily determined by soil type, with plant species having a stronger influence on the microbial diversity and composition than rhizocompartment and soil pollution level. We found that different HM accumulating plants harbored a unique set of core taxa in the rhizosphere with Sphingomonas and Burkholderiaceae shared among them. Use of RNA-SIP further revealed that the core rhizosphere taxa phylogenetically overlapped with the active rhizobacteria feeding on carbon-rich rhizodeposits, suggesting that the specific root exudate components driving the core microbiomes may be common across different plant species. Several keystone taxa were part of the core microbiota and facilitated plant metal tolerance and accumulation when inoculated with SynCom comprising the core cohorts.Conclusions: Our results suggest that a conserved core root microbiota has evolved with HM accumulating plants via root metabolic cues and exhibited potential to increase plant fitness and phytoextraction of HM. This study has important implications for harnessing the persistent microbiome members to improve host performance and accelerate the plant-assisted restoration of contaminated soil ecosystems.