Microbial communities associated with Arabidopsis roots and rhizoplane subjected to a severe drought event and impact of a consortium on alleviating that stress.

Drought puts a major restriction on plant production and the current effects of global warming are further enhancing drought stress for crops. There is increasing information about the ability of specific soil microbes to affect stress tolerance in plants. Here we show that a four-species bacterial consortium (Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus, termed as SPMX for short), which iswas able to synergistically produce more biofilm biomass together than the sum of the four single-species cultures, significantly improved Arabidopsis survival rate during water deprivation whereas no drought-tolerant effects were observed when subjected to the individual strains. The underlying mechanisms were found to be associated with enhanced leaf chlorophyll content, promoting plant performance, enhancing endogenous abscisic acid (ABA) signaling and alleviating water stress by SPMX. SPMX abundance was promoted in the plant root area during drought compared to normal conditions. Our data also showed that SPMX stabilized the bacterial community composition during drought, and enhanced the abundance of Actinobacteria, which jointly conferred an increased drought tolerance to plants.