Biosynthesis of silver nanoparticle from pomelo (Citrus Maxima) and their antibacterial activity against acidovorax oryzae RS-2

Silver nanoparticles (AgNPs), synthesized with plant materials, are considered to be an emerging field of agriculture for their eco-friendly and outstanding antibacterial attributes. In this study, we synthesized AgNPs using pomelo (Citrus maxima) fruit extract as a biological capping and reducing material. The particle size was determined as 11.3-12.8 nm by using UV-vis spectrophotometer, TEM and x-ray diffraction analysis. UV-vis spectrophotometer analysis also confirmed the formation of AgNPs in colloidal solution and showed a maximum absorption at 426 nm. Fourier transform infrared spectra was used to analysed the involvement of biological molecule in AgNPs synthesis. The minimum inhibitory concentration of AgNPs against Acidovorax oryzae strain RS-2 was determined as 25 mu g ml(-1) by agar well diffusion and bacterial growth assay. In addition, bacterial viability and swarming motility were significantly inhibited by AgNPs. Compared with the control, 25 mu g ml(-1) of AgNPs lower bacterial biofilm formation up to 68.24%. The bacterial cell wall damaged by AgNPs was observed t TEM. Furthermore, AgNPs treatment resulted into the down regulation of expression of many type VI secretion system related genes, suggesting that AgNPs also have an effect on the virulence of bacteria. The overall conclusion of this study suggests that AgNPs can play an important role in controlling A. oryzae.