Novel PGPR manipulate host plant fitness

Plants are constantly challenged by abiotic and biotic stresses. Failure to overcome these stresses could lead to the lack of plant fitness and significant yield losses. Plant-growth-promoting rhizobacteria (PGPR) are known for their microbial products that stimulate plant growth and many of those effective microbial products have been commercially marketed. However, the precise roles of PGPR in plant fitness improvement are still unknown. Beneficial bacteria in the genus Bacillus are ubiquitous in nature and are well known for their ecological, clinical, and industrial values. Here we identified one novel Bacillus spp. strain XY44 that effectively promotes plant health. XY44 was originally isolated from the root microbiome of switchgrass plants that exhibited better fitness. We found that XY44 treatment could not only increase plant biomass but also showed potentials in fungal pathogen antagonism and plant abiotic stress regulation. Furthermore, the RNA-seq data indicated highly differentially gene expression in host plants due to soil drench with XY44. It seems that leaf tissues and root tissues have different response patterns to the employment of beneficial bacteria. Overall, our results uncovered how members of PGPR are likely to function in plant fitness, possibly by activating abiotic and/or biotic stress responses of host plants. The outcomes of this research would lead to a better and deeper understanding of plant fitness promotion induced by beneficial microbes and provide insights and strategies for the development of sustainable agriculture. This novel PGPR XY44 could also be incorporated into cultural practice as a novel biological control agent.