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Various antibacterial mechanisms of biosynthesized copper oxide nanoparticles against soilborne Ralstonia solanacearum

Chen, Juanni, Mao, Shuyu, Xu, Zhifeng, Ding, Wei
RSC advances 2019 v.9 no.7 pp. 3788-3799
Ralstonia solanacearum, absorption, adenosine triphosphate, antibacterial properties, bacteria, bacterial motility, bacterial wilt, biofilm, copper, copper nanoparticles, cupric oxide, disease control, disease occurrence, gene expression regulation, genes, greenhouse production, greenhouses, irrigation, leaf extracts, pathogenesis, plant pathogens, soil-borne diseases, tobacco, transmission electron microscopy, virulent strains
The substantial antimicrobial efficacy of nanoparticles against phytopathogens has been extensively investigated for advanced agricultural applications. However, few reports have focused on soilborne pathogenic bacteria. The aim of this study was to obtain sustainably synthesized copper oxide nanoparticles (CuONPs) using papaya leaf extracts and investigate the bactericidal activity of these CuONPs against Ralstonia solanacearum, the cause of bacterial wilt, under laboratory and greenhouse conditions. The results showed that CuONPs possessed strong antibacterial activity and that all R. solanacearum were killed after exposure to 250 μg mL⁻¹ CuONPs. CuONPs could interact with bacterial cells to prevent biofilm formation, reduce swarming motility and disturb ATP production. Ultrastructural observations by transmission electron microscopy (TEM) revealed that after interactions with CuONPs, bacterial cells suffered significantly from nanomechanical damage to the cytomembrane, accompanied by the absorption of multiple nanoparticles. In addition, molecular studies identified the downregulation mechanism of a series of genes involving pathogenesis and motility. The control efficiency of CuONPs in tobacco bacterial wilt disease management under greenhouse conditions was verified by root irrigation application, demonstrating that as-prepared CuONPs significantly reduced the disease occurrence and disease index. Our studies focused on developing biosynthesized nanoparticles as a biocompatible alternative for soilborne disease management.