Green Synthesis of Silver Nanoparticles with Culture Supernatant of a Bacterium Pseudomonas rhodesiae and Their Antibacterial Activity against Soft Rot Pathogen Dickeya dadantii

Abstract

Bacterial stem and root rot disease of sweet potato caused by Dickeya dadantii recently broke out in major sweet potato planting areas in China and calls for effective approaches to control the pathogen and disease. Here, we developed a simple method for green synthesis of silver nanoparticles (AgNPs) using bacterial culture supernatants. AgNPs synthesized with the cell-free culture supernatant of a bacterium Pseudomonas rhodesiae displayed the characteristic surface plasmon resonance peak at 420–430 nm and as nanocrystallites in diameters of 20–100 nm determined by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction spectroscopy. Functional groups associated with proteins in the culture supernatant may reduce silver ions and stabilize AgNPs. The AgNPs showed antibacterial activities against D. dadantii growth, swimming motility, biofilm formation, and maceration of sweet potato tubers whereas the culture supernatant of P. rhodesiae did not. AgNPs (12 µg∙ml−1) and AgNO3 (50 µg∙ml−1) showed close antibacterial activities. The antibacterial activities increased with the increase of AgNP concentrations. The green-synthesized AgNPs can be used to control the soft rot disease by control of pathogen contamination of sweet potato seed tubers.

Green-Synthesization of Silver Nanoparticles Using Endophytic Bacteria Isolated from Garlic and Its Antifungal Activity against Wheat Fusarium Head Blight Pathogen Fusarium graminearum

“…These bacteria have been used as a biological source in the biosynthesis of AgNPs, but the mechanism of bacteria for AgNPs biosynthesis is still unknown. Interestingly, a lot of previous reports have revealed the existence of various biomolecules that are produced by bacteria such as alkaloids, phenolic compounds, enzymes, co-enzymes, proteins, amino acids, polysaccharides, and vitamins, all of which have been able to act as effective agents for converting Ag + to Ag 0 [19,20,29,30]. Therefore, it could be inferred that these biomolecules that are produced by bacteria may play a key role in the mediation of AgNPs biosynthesis.…”

“…For example, silver nanoparticles (AgNPs) have been shown to significantly inhibit the hyphal growth of a variety of foliar and soil-borne plant pathogen [14,15]. In addition, more and more attention has been paid to the biosynthesis of AgNPs by using eco-friendly materials, such as plant extracts and microorganisms, which are safer than traditional physical and chemical methods [16][17][18][19].…”

Lemon-Fruit-Based Green Synthesis of Zinc Oxide Nanoparticles and Titanium Dioxide Nanoparticles against Soft Rot Bacterial Pathogen Dickeya dadantii

“…Dry lemon powder, ZnONP powder, and TiO 2 NP powder were analyzed by Fourier transform infrared (FTIR) spectroscopy to detect groups responsible for synthesis and stabilizing ZnONPs and TiO 2 NPs as previously described [41]. Bruker infrared table (Bruker Optics Inc. Billerica, MA, USA) and LibreTexts infrared spectroscopy absorption table (https://chem.libretexts.org/) were used to interpret the FTIR spectra.…”

“…Bruker infrared table (Bruker Optics Inc. Billerica, MA, USA) and LibreTexts infrared spectroscopy absorption table (https://chem.libretexts.org/) were used to interpret the FTIR spectra. The elements of ZnONPs and TiO 2 NPs were detected by energy dispersive X-ray spectroscopy [41]. The size and morphology and the crystalline nature of ZnONPs and TiO 2 NPs were observed and analyzed by transmission electron microscopy (TEM), scanning electron microscopy, and X-ray diffraction spectroscopy [41].…”

“…Antibacterial activities against D. dadantii were first detected by the diffusion assay with agar plates [41]. Dickeya dadantii suspension was inoculated into the nutrient agar to 10 7 cells•mL −1 .…”