Biosynthesis of Silver Chloride Nanoparticles by Rhizospheric Bacteria and Their Antibacterial Activity against Phytopathogenic Bacterium Ralstonia solanacearum.

Iman Sabah Abd Alamer,Bin Li,Temoor Ahmed,Ali Athafah Tomah,Jingze Zhang

doi:10.3390/molecules27010224

Abstract

Ralstonia solanacearum is the most destructive pathogen, causing bacterial wilt disease of eggplant. The present study aimed to develop green synthesis and characterization of silver chloride nanoparticles (AgCl-NPs) by using a native bacterial strain and subsequent evaluation of their antibacterial activity against R. solanacearum. Here, a total of 10 bacterial strains were selected for the biosynthesis of AgCl-NPs. Among them, the highest yield occurred in the synthesis of AgCl-NPs using a cell-free aqueous filtrate of strain IMA13. Ultrastructural observation revealed that the AgCl-NPs were spherical and oval with smooth surfaces and 5–35 nm sizes. XRD analysis studies revealed that these particles contained face-centered cubic crystallites of metallic Ag and AgCl. Moreover, FTIR analysis showed the presence of capping proteins, carbohydrates, lipids, and lipopeptide compounds and crystalline structure of AgCl-NPs. On the basis of phylogenetic analysis using a combination of six gene sequences (16S, gyrA, rpoB, purH, polC, and groEL), we identified strain IMA13 as Bacillus mojavensis. Three kinds of lipopeptide compounds, namely, bacillomycin D, iturin, and fengycin, forming cell-free supernatant produced by strain IAM13, were identified by MALDI-TOF mass spectrometry. Biogenic AgCl-NPs showed substantial antibacterial activity against R. solanacearum at a concentration of 20 µg/mL−1. Motility assays showed that the AgCl-NPs significantly inhibited the swarming and swimming motility (61.4 and 55.8%) against R. solanacearum. Moreover, SEM and TEM analysis showed that direct interaction of AgCl-NPs with bacterial cells caused rupture of cell wall and cytoplasmic membranes, as well as leakage of nucleic acid materials, which ultimately resulted in the death of R. solanacearum. Overall, these findings will help in developing a promising nanopesticide against phytopathogen plant disease management.

Highlights

Ralstonia solanacearum is a soilborne Gram-negative bacterium that causes plant diseases mainly in tropical and subtropical climates [1]
The experimental results showed that the obvious color change appeared only in the solution with the cell-free culture supernatant (CFCS) produced by strain IMA13 and AgNO3 (Figure 1b), indicating the formation of AgCl-NPs after incubation for 48 h
We reported the biological, eco-friendly, and non-toxic method for the synthesis of AgCl-NPs using cell-free culture supernatant of bacterial strain IMA13

Summary

Introduction

Ralstonia solanacearum is a soilborne Gram-negative bacterium that causes plant diseases mainly in tropical and subtropical climates [1]. In addition to the polar flagella responsible for swimming motility, the pathogen produces type IV pili (TFP) that govern twitching motility, which is required for plant colonization and full Virulence [7]. These characters have contributed to the ranking of R. solanacearum as one of the most destructive plant-pathogenic bacterial species worldwide [8]. Some of the biocontrol products in use were limited by geographical location due to the properties of biocontrol agents These invited researchers to devise a new strategy to treat the plant diseases that plant pathogens caused, known as the biosynthesis of green nanoparticles [10]

Methods

Results

Conclusion