Antibacterial and antivirulence activity of biosynthesized silver nanoparticles by Pseudomonas lurida against several plant pathogenic bacteria

In recent years, the synthesis of metal nanoparticles using bacteria has been extensively studied and recognized as a non-toxic and efficient method applicable in the control of bacterial pathogens. This study aims to investigate the potential of endophytic bacteria in synthesizing silver nanoparticles (AgNPs), characterize the produced silver nanoparticles, and their antibacterial activity. Pseudomonas lurida Bi6 was able to biosynthesize AgNPs. Scanning electron microscopy (SEM) showed that biosynthesized AgNPs exhibited a spherical shape with an average size of 37 nm. Additionally, the biosynthesized silver nanoparticles were evaluated for their antibacterial activity against various bacterial pathogens. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AgNPs against Pseudomonas tolaasii, Ralstonia solanacearum, and Agrobacterium tumefaciens were 25, 50, and 50μg/ml, respectively. The biosynthesized AgNPs showed an MBC value of 50, 100, and 100 µg/ml against P. tolaasii, R. solanacearum, and A. tumefaciens, respectively. At sub-MIC concentrations, AgNPs showed various negative effects on virulence traits of all three pathogens, such as motility behaviors, chemotaxis, exopolysaccharide production, and biofilm formation that is important for pathogenicity. The SEM micrographs revealed that biosynthesized AgNPs enhance various morphological abnormalities in the treated cells. Our study indicates that biosynthesized AgNPs exhibit strong antibacterial activity against bacterial pathogens studied. Information on the mechanisms mediated by AgNPs as an eco-friendly and safe tool against bacterial pathogens is important to the design of new and more efficient disease control strategies. However, field experiments need to be performed under controlled conditions to scale up the current work and find out the efficacy of AgNPs on a larger scale.