Pseudomonas sp. N5.12 Metabolites Formulated in AgNPs Enhance Plant Fitness and Metabolism Without Altering Soil Microbial Communities

This study investigated the effects of metabolites from the beneficial bacteria <i>Pseudomonas</i> N5.12 formulated as silver nanoparticles (AgNPs) on tomato plants and soil microbial communities to explore the environmental safety of AgNPs for future applications in agriculture. AgNPs coated with bacterial metabolites exhibit biological activity that is dose-dependent, as shown by cytoskeleton alterations in Arabidopsis roots. The results show that N5.12-AgNPs can trigger beneficial effects on tomato plants, either when delivered through the leaves or roots, indicating the effectiveness of the metabolites formulated as NP. These effects consist of lowering oxidative stress metabolism and, therefore, improving plant resilience and increasing chlorophyll <i>a</i> and carotenoid content. The significant reduction in H₂O₂ content was not associated with ROS-scavenging enzymes but with an increase in total phenolic content. In contrast, AgNPs had a minimal impact on bacterial metabolic activity, irrespective of the application method. The structure of microbial communities was not altered by AgNPs, indicating environmental safety for agronomic applications. These findings suggest that <i>Pseudomonas</i> N5.12 metabolites formulated in AgNPs at physiological concentrations (30 ppm) may offer agricultural benefits by improving plant health and appearing as an environmentally safe alternative for agriculture.