Ag/SiO2 nanocomposite mediated by Escherichia coli D8 and their antimicrobial potential

Abstract

Silica (SiO2) has a fundamental role in the recuperation of plants in response to environmental stresses, besides the induction of resistance against plant diseases. Silver nanoparticles (AgNPs) have a superior antimicrobial activity. The combination between SiO2 and AgNPs is a promising approach due to their antimicrobial activity, biological activity, low toxicity, and high stability of the produced nanocomposite. The current study postulated a green method for silver/silica nanocomposite (Ag/SiO2NC) synthesis at room temperature using the crude metabolites of Escherichia coli D8 (MF062579) strain in the presence of sunlight. UV-Vis spectrophotometry, X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) analyses have characterized the biosynthesized nanocomposite. TEM study of Ag/SiO2NC showed an average particle size of ~32 – 48 nm whereas AgNPs showed a mean size of 18 – 24 nm. The negative charged Ag/SiO2NC (-31.0 mV) showed potent antimicrobial activity against Bacillus cereus ATCC6633, Klebsiella pneumoniae ATCC33495, Staphylococcus aureus (ATCC25923), E. coli (ATCC25922), Candida albicans (ATCC10231), and Botrytis cinerea (Pers: Fr.). The minimum inhibitory concentration (MIC) test showed a dose-dependent manner of Ag/SiO2NC antimicrobial action. MIC values of Ag/SiO2NC against the tested pathogens exhibited 125 and 6.25 μg.mL-1 as antibacterial and antifungal agents, respectively. TEM micrographs showed changes in the pathogens treated with Ag/SiO2NC including wrinkling, damage, and rupture of the bacterial cell membrane. In addition, the formation of a mucilage matrix connecting the hyphal cells, the appearance of big vacuoles and lipid droplets with severe leakage of cytoplasmic contents of the treated B. cinerea were also recorded.

Synthesis, Characterization, Antimicrobial and Electrochemical Studies of Biosynthesized Zinc Oxide Nanoparticles Using the Probiotic Bacillus Coagulans (Atcc 7050)

“…). While B. subtilis ZBP4 biosynthesized ZnO NPs with irregular spherical shape and size range of 22-59 nm as reported by Hamk et al(2022). The current results confirmed the high stability of the biosynthesized ZnO NPs due to the high repulsion forces between the particles due to its high surface positive charge values which prevent their aggregation and agglomeration.…”

Antifungal activity of silver/silicon dioxide nanocomposite on the response of faba bean plants (Vicia faba L.) infected by Botrytis cinerea

“…Rodrigues et al ( 2020 ) demonstrated the biosynthesis of Ag/SiO 2 NC with AgNPs with a mean size of 45 ± 12 nm and a negative charge (− 35.5) using green tea extract. The positive charge of the nanomaterials increases the effective electrostatic association with the microbial cell wall's negative charges, allowing them to easily penetrate the cell membrane (El-Zahed et al 2022 ). FTIR and XRD results stated the purity of Ag/SiO 2 NC particles that formed exclusively from Si, oxygen and silver, which was in concurrence with Jeon et al ( 2003 ) and Wei et al ( 2014 ) results.…”

“…Ag/SiO 2 NC was prepared according to Sadeghi et al ( 2013 ) and modified by El-Zahed et al ( 2022 ). Briefly, AgNPs were biosynthesized in the presence of sunlight by mixing free-cell supernatant of E. coli D8 (filtered from overnight bacterial growth, inoculated by a 0.5 McFarland standard, 1–2 × 10 8 CFU/ml) with 1.5 mM of AgNO 3 solution (1:1 v/v).…”

Antimicrobial Activity of N‐Substituted Derivatives of 5‐Chloro‐2,3‐ Diphenyl Indole

“…A 0–10 mg/ml series from each compound was prepared, added separately into 0.5 MacFarland inoculated MHB and incubated at 37 °C or 28 °C for 24 hours or 7 days. After incubation, the microbial growth rates were measured spectrophotometrically at 600 nm [48] …”