Emergent bacterial community properties induce enhanced drought tolerance in Arabidopsis

Drought severely restricts plant production and global warming is further increasing drought stress for crops. Much information reveals the ability of individual microbes affecting plant stress tolerance. However, the effects of emergent bacterial community properties on plant drought tolerance remain largely unexplored. Here, we inoculated Arabidopsis plants in vivo with a four-species bacterial consortium (Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans, and Paenibacillus amylolyticus, termed as SPMX), which is able to synergistically produce more biofilm biomass together than the sum of the four single-strain cultures, to investigate its effects on plant performance and rhizo-microbiota during drought. We found that SPMX remarkably improved Arabidopsis survival post 21-day drought whereas no drought-tolerant effect was observed when subjected to the individual strains, revealing emergent properties of the SPMX consortium as the underlying cause of the induced drought tolerance. The enhanced drought tolerance was associated with sustained chlorophyll content and endogenous abscisic acid (ABA) signaling. Furthermore, our data showed that the addition of SPMX helped to stabilize the diversity and structure of root-associated microbiomes, which potentially benefits plant health under drought. These SPMX-induced changes jointly confer an increased drought tolerance to plants. Our work may inform future efforts to engineer the emergent bacterial community properties to improve plant tolerance to drought.