Genome sequencing and broad-spectrum plant growth-promoting effects of the multifunctional PGPR strain Priestia aryabhattai B8.

Abstract

A multifunctional plant growth-promoting bacterial strain designated as B8 was isolated from the rhizosphere soil of tobacco under continuous cropping. According to morphological, biochemical, and physiological characteristics, and supported by genomic phylogenetic analysis, the strain was identified as Priestia aryabhattai. Phenotypic assays showed that B8 exhibits multiple plant growth-promoting traits, including indole-3-acetic acid (IAA) production, phosphate and potassium solubilization, and siderophore production. Whole-genome sequencing and functional annotation revealed that the genome of B8 consists of one circular chromosome and two plasmids, harboring a complete tryptophan biosynthesis pathway (trpABCDEF), a phosphate-specific transport system (pstSABC), potassium transporter genes (khtT/khtU), and a siderophore biosynthetic gene cluster. Additionally, genes encoding carbohydrate-active enzymes, such as chitinases and β-glucanases involved in cell wall degradation, along with multiple secondary metabolite biosynthetic gene clusters, were identified, providing a molecular basis for its multifunctional plant growth-promoting and biocontrol potential. Pot experiments indicated that inoculation with strain B8 was associated with significantly increased contents of IAA, available phosphorus, and available potassium in the rhizosphere soils of tobacco, pak choi, and wheat, as well as enhanced plant growth and root development. Field trials further suggested that B8 treatment correlated with significantly improved tobacco plant height, stem circumference, and maximum leaf area, along with elevated contents of total sugar, reducing sugar, and potassium in tobacco leaves. Multivariate statistical analyses pointed to soil available phosphorus, available potassium, and IAA content as key factors driving crop growth. This study provides insights into the multifunctional mechanisms of Priestia aryabhattai B8, offering a theoretical foundation and microbial resource for biofertilizer development.IMPORTANCEThis work advances sustainable agriculture by introducing a multifunctional soil bacterium, Priestia aryabhattai B8, as an eco-friendly alternative to reduce reliance on chemical fertilizers. By demonstrating that this single strain enhances the growth and quality of diverse crops, including tobacco, pak choi, and wheat, in pot experiments and by further validating its growth-promoting effects on tobacco in the field, this research confirms the practical potential of beneficial microbes for improving crop productivity. The comprehensive genomic and functional insights gained into the bacterium's nutrient-solubilizing and hormone-producing mechanisms provide a solid foundation for designing robust and predictable biofertilizers. Overall, this investigation contributes to lowering chemical inputs, restoring soil fertility, and promoting environmentally sustainable food production systems.