Genomic insights into Serratia bockelmanii strain 201: unlocking its potential for plant growth promotion and salt stress tolerance.

This study investigated Serratia bockelmanii sp. 201 (strain C2), a bacterium isolated from the rhizosphere of Opuntia ficus-indica. This strain demonstrates relevant plant growth-promoting (PGP) traits and enhances salt stress tolerance in crops. While its phenotypic characteristics have been documented, the genomic basis of these traits remains unexplored. Whole genome sequencing of the strain C2 revealed a 5.24 Mbp circular chromosome with 59.18% GC content, encoding 4,841 protein-coding genes. Pan-genome analysis demonstrated a 99.06% average nucleotide identity (ANI) with Serratia bockelmanii. Functional genomic annotation identified key plant growth-promoting (PGP) genes, including those involved in phosphate solubilization, siderophore biosynthesis, indole-3-acetic acid (IAA) production, and volatile organic compound (VOC) synthesis. Notably, the genome lacked high-risk antimicrobial resistance (AMR) genes while possessing genes associated with stress tolerance. Furthermore, WGS illuminated the pathways and regulatory networks employed by strain C2 to synthesize various growth regulators, enhance nutrient availability, and consequently promote plant health and stress tolerance, with tomato seedling assays specifically confirming VOC-mediated salt stress alleviation by this strain. This study provides the first genomic evidence for the multifunctional PGP traits and salt stress mitigation mechanisms of Serratia bockelmanii sp. 201. The absence of pathogenic markers supports its potential as a safe biofertilizer for saline agriculture. Moreover, in vitro tomato growth assays demonstrate the beneficial effects of VOCs emitted by Serratia bockelmanii sp. 201. Further studies are needed to profile these VOCs and to validate the performance of this PGPR strain under stress conditions in greenhouse and field trials.