Integrated genomic and mutagenesis analysis of Pseudomonas argentinensis SA190 reveals mechanisms of plant root colonization and stress resilience.

BACKGROUND: Pseudomonas argentinensis SA190 is a desert-adapted, plant-associated bacterium with demonstrated potential to enhance plant growth under abiotic stress. In this study, we conducted a comprehensive genomic and functional characterization of SA190 to uncover the molecular mechanisms underlying its biofilm formation, root colonization, and plant growth-promoting traits. RESULTS: The SA190 genome consists of a single circular chromosome (5.07 Mb, 64% GC) encoding 4561 predicted ORFs. Functional annotation revealed genes related to phosphate solubilization (pqq operon), antifungal activity, and stress mitigation, including ACC deaminase. AntiSMASH analysis identified eight biosynthetic gene clusters linked to secondary metabolite production, including siderophores, terpenes, and β-lactones. Metabolic profiling demonstrated selective utilization of root exudate-associated sugars, consistent with rhizosphere adaptation. By a Tn5 transposon mutagenesis approach, we identified key regulators required for biofilm formation. Biofilm mutants deficient in wspC, rpoE, and fliD were differentially compromised in plant colonization and plant growth promotion under ambient and/or drought conditions. CONCLUSION: Our study suggests that SA190 is a metabolically streamlined yet ecologically versatile PGPB and provides functional insights into its potential application as a bioinoculant for sustainable agriculture in arid environments.