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.
Highlights
Gram-negative bacteria belonging to the genera Pectobacterium and Dickeya are broad-host-range pathogens causing devastating soft rot diseases of ornamental and crop plants [1,2]
AgNPs were synthesized by incubation of AgNO3 with CFCS of P. rhodesiae G1 and
The success and failure of production of AgNPs by incubation of AgNO3 with CFCS of different strains suggest that the components of CFCS determine the green synthesis of AgNPs
Summary
Gram-negative bacteria belonging to the genera Pectobacterium and Dickeya are broad-host-range pathogens causing devastating soft rot diseases of ornamental and crop plants [1,2]. Outbreaks of soft rot diseases of staple food crops in the last two decades worldwide indicate the failure in management of soft rot Pectobacterium and Dickeya. Crop varieties resistant to soft rot Molecules 2019, 24, 2303; doi:10.3390/molecules24122303 www.mdpi.com/journal/molecules. Pectobacterium and Dickeya are lacking while large-scale use of effective antibiotics is no longer allowed in fields due to the risks of introducing resistance to bacterial pathogens of humans or animals [2]. Using nanoparticles as novel antimicrobial agents against broad-spectrum microbes including Gram-positive and Gram-negative multidrug-resistant bacteria, fungi, protozoa, and viruses has brought revolutions in the field of health, food, and agriculture technology
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